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Title: An Introduction to Entomology: Vol. 4

Author: William Kirby
William Spence

Release date: August 27, 2013 [eBook #43579]
Most recently updated: October 23, 2024

Language: English

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*** START OF THE PROJECT GUTENBERG EBOOK AN
INTRODUCTION TO ENTOMOLOGY: VOL. 4 ***

Painted by J. J. Masquerier. Engraved by W. T. Fry.

William Spence, Esqr., F.L.S.

Published by Longman & Co. London, July 1825.

AN

INTRODUCTION
TO

ENTOMOLOGY:
OR

ELEMENTS

OF THE

NATURAL HISTORY OF INSECTS:

WITH PLATES.

By WILLIAM KIRBY, M.A. F.R. and L.S.

RECTOR OF BARHAM,
AND

WILLIAM SPENCE, Esq. F.L.S.

IN FOUR VOLUMES.

VOL. IV.

FIFTH EDITION.

LONDON:
PRINTED FOR

LONGMAN, REES, ORME, BROWN, AND GREEN,

PATERNOSTER ROW.

1828.

PRINTED BY RICHARD TAYLOR,

RED LION COURT, FLEET STREET.

CONTENTS OF VOL. IV.
Letter. Page.

XXXVII. Internal Anatomy and Physiology of
Insects. Sensation 1-33

XXXVIII. Internal Anatomy and Physiology of
Insects continued. Respiration 34-80

XXXIX. Internal Anatomy and Physiology of
Insects continued. Circulation 81-101

XL. Internal Anatomy and Physiology of
Insects continued. Digestion 102-126

XLI. Internal Anatomy and Physiology of
Insects continued. Secretion 127-151

XLII. Internal Anatomy and Physiology of
Insects continued. Reproduction 152-173

XLIII. Internal Anatomy and Physiology of
Insects concluded. Motion 174-203

XLIV. Diseases of Insects 204-240

XLV. Senses of Insects 241-264

XLVI. Orismology, or Explanation of Terms 265-363

XLVII. System of Insects 364-428

XLVIII. History of Entomology 429-485

XLIX. Geographical Distribution of Insects;
their Stations and Haunts;
Seasons; Times of Action and
Repose 486-527

L. On Entomological Instruments; and
the best Methods of collecting,
breeding, and preserving Insects 528-559

LI. Investigation of Insects 560-573

Appendix 575-584
Authors quoted 585-602
Explanation of the Plates 603-614
Indexes 615-683

AN INTRODUCTION TO ENTOMOLOGY.

LETTER XXXVII.
INTERNAL ANATOMY AND PHYSIOLOGY OF INSECTS.
SENSATION.

Having given you this full account of the external parts of insects, and their
most remarkable variations; I must next direct your attention to such
discoveries as have been made with regard to their Internal Anatomy and
Physiology: a subject still more fertile, if possible, than the former in
wonderful manifestations of the power, wisdom and goodness of the
Creator.
The vital system of these little creatures, in all its great features, is perfectly
analogous to that of the vertebrate animals. Sensation and perception are by
the means of nerves and a common sensorium; the respiration of air is
evident, being received and expelled by a particular apparatus; nutrition is
effected through a stomach and intestines; the analogue of the blood
prepared by these organs pervades every part of the body, and from it are
secreted various peculiar substances; generation takes place, and an
intercourse between the sexes, by means of appropriate organs; and lastly,
motion is the result of the action of muscles. Some of these functions are,
however, exercised in a mode apparently so dissimilar from what obtains in
the higher animals, that upon a first view we are inclined to pronounce them
the effect of processes altogether peculiar. Thus, though insects respire air,
they do not receive it by the mouth, but through little orifices in the sides of
the body; and instead of lungs, they are furnished with a system of air-
vessels, ramified ad infinitum, and penetrating to every part and organ of
their frame; and though they are nourished by a fluid prepared from the
food received into the stomach, this fluid, unlike the blood of vertebrate
animals, is white, and the mode in which it is distributed to the different
parts of the system, except in the case of the true Arachnida, in which a
circulation in the ordinary way has been detected, is altogether obscure.

In order that you may more clearly understand the variations that occur in
insects, and in what respects they differ amongst themselves, and from the
higher animals, in the vital functions and their organs, I shall consider them
as to their organs of sensation, respiration, circulation, nutrition,
generation, secretion, and muscular motion.

Organs of Sensation.—The nervous system of animals is one of the most
wonderful and mysterious works of the Creator. Its pulpy substance is the
visible medium by which the governing principle[1] transmits its commands
to the various organs of the body, and they move instantaneously—yet this
appears to be but the conductor of some higher principle, which can be
more immediately acted upon by the mind and by the will. This principle,
however, whatever it be, whether we call it the nervous fluid, or the nervous
power[2], has not been detected, and is known only by its effects. The
system of which we are speaking may therefore be deemed the foundation
and root of the animal, the centre from which emanate all its powers and
functions.
Comparative anatomists have considered the nervous system of animals as
formed upon four primary types, which may be called the molecular, the
filamentous, the ganglionic, and cerebro-spinal[3]. The first is where
invisible nervous molecules are dispersed in a gelatinous body, the
existence of which has only been ascertained by the nervous irritability of
such bodies, their fine sense of touch, their perceiving the movements of the
waters in which they reside, and from their perfect sense of the degrees of
light and heat[4]. Of this description are the infusory animals, and the
Polypi. The nervous molecules in these are conjectured to constitute so
many ganglions, or centres of sensation and vitality[5]. The second, the
filamentous, is where the nervous system consists of nervous threads
radiating from the mouth, as in the Radiata, or star-fish and sea-urchins[6].
The third, the ganglionic, is where the nervous system consists of a series of
ganglions connected by nervous threads or a medullary chord, placed,

except the first ganglion, below the intestines, from which proceed nerves
to the various parts of the body. This system may be considered as divisible
into two—the proper ganglionic, in which it is ganglionic with the
ganglions arranged in a series with a double spinal chord. This prevails in
the classes Insecta, Crustacea, Arachnida, &c., and the improper
ganglionic, in which it is ganglionic with the ganglions dispersed
irregularly, but connected by nervous threads, as in the Mollusca[7]. In the
fourth, the cerebro-spinal, the nervous tree may be said to be double, or to
consist of two systems—the first taking its origin in a brain formed of two
hemispheres contained in the cavity of the head, from which posteriorly
proceeds a spinal marrow, included in a dorsal vertebral column. These
send forth numerous nerves to the organs of the senses and the muscles of
the limbs. The second consists of two principal ventral chords, which by
their ganglions, but without any direct communication, anastomose with the
spinal nerves and some of those of the brain, and run one on each side from
the base of the skull to the extremity of the sacrum. This system consists of
an assemblage of nervous filaments bearing numerous ganglions, from
which nervous threads are distributed to the organs of nutrition and
reproduction[8]. Its chords are called the great sympathetic, the intercostal,
or trisplanchnic nerves[9]. While the first of these two systems is the
messenger of the will, by means of the organs of the senses connects us
with the external world, and is subject to have its agency interrupted by
sleep or disease[10]; the latter is altogether independent of the will and of the
intellect, is confined to the internal organic life, its agency continues
uninterrupted during sleep, and is subject to no paralysis. While the former
is the seat of the intellectual powers, the latter has no relation to them, but is
the focus from whence instincts exclusively emanate: from it proceed
spontaneous impulses and sympathies, and those passions and affections
that excite the agent to acts in which the will and the judgement have no
concern[11].
It is probable, though the above appear to exhibit the primary types of
nervous systems, that others exist of an intermediate nature, with which
future investigators may render us better acquainted[12]: but as our business
is solely with that upon which insects in this respect have been modelled,
without expatiating further in this interesting field, I shall therefore now
confine myself to them.

We have before seen[13] that the nervous system of insects belongs to the
ganglionic type: but it requires a more full description, and this is the place
for it. It originates in a small brain placed in the head, and consisting almost
universally of two lobes, sometimes extremely distinct. It is placed over or
upon the œsophagus or gullet, and from its posterior part proceeds a double
nervous chord, which embracing that organ as a collar dips below the
intestines, and proceeds towards the anus, forming knots or ganglions at
intervals, in many cases corresponding in number with the segments of the
body, and sending forth nerves in pairs, the ramifications of which are
distributed to every part of the frame. In the perfect insect the bilobed
ganglion of the head or the brain is usually of greater volume than in the
larva, and the ganglions of the spinal chord are fewer, which gives a more
decided character of centricity to the whole nervous system[14]. This may be
considered more particularly with respect to its substance and colour; its
tunics, and parts.
I. Substance and Colour.—The nervous apparatus of insects is stated by
those who have examined it most narrowly, though consisting of a cortical
and medullary part, the latter more delicate and transparent than the former,
to be less tender and less easy to separate than the human brain[15]. It has a
degree of tenacity, and does not break without considerable tension; in
general, it is clammy and flabby, and under a microscope a number of
minute grains are discoverable in it, and when left to dry upon glass, it
appears to contain a good deal of oil, which does not dry with the rest[16].
That of the ganglions differs from the substance of the rest of the spinal
chord, in being filled with very fine aërial vessels, which are not
discoverable in the latter[17]. With regard to colour, Lyonet states that the
chords of the spinal marrow in the larva of the great goat-moth are of a
blueish gray, and have some transparence[18]; Malpighi and Swammerdam
observed that the cortical part of the ganglions of that of the silk-worm and
the hive-bee had a reddish hue, while the medullary part was white[19];
Cuvier relates that the brain and the third ganglion in Hypogymna dispar,
with us a scarce moth, differed in colour from all the rest, being quite white,
while the others were more or less tinted, and examined under a lens
appeared variegated by reddish sinuous markings, resembling blood vessels
as they are seen in injected glands[20].

II. Tunics.—The coats that inclose the various branches of the nervous
system in insects seem analogous to those of vertebrate animals. The first
thing that strikes the eye, when these parts in a recent subject are submitted
to a microscope, is a tissue of very delicate vessels, which ramify beyond
the reach of the assisted sight; these are merely air-vessels or bronchiæ
derived originally from the tracheæ of the animal: but besides these is an
exterior and an interior tunic; the first corresponding with the dura mater of
anatomists; and the other, which is the most delicate and incloses the
cortical and medullary parts, with the pia mater[21].
III. Parts.—The nervous system of insects consists of the brain; the spinal
marrow and its ganglions; and the nerves.

i. Brain.[22] Linné denied the existence of a brain in insects, and most
modern physiologists seem to be of the same opinion. A part however,
analogous to this important organ—at least in its situation, and in its
emission of nerves to the principal organs of the senses, in which respect it
certainly differs very materially from the upper cervical ganglion, which Dr.
Virey regards as its analogue[23]—is certainly to be found in them; and as
Messrs. Cuvier and Lamarck distinguish this part by the name of brain, we
may continue to call it by that name without impropriety. The brain of
insects, then, is distinguished from the succeeding ganglions of the spinal
chord by its situation in the head, the middle of the internal cavity of which
it occupies, and by being the only ganglion above the œsophagus. It is
usually small, though in some cases larger than they are[24]. It consists of
two lobes, more or less distinct and generally of a spherical form. In
Oryctes nasicornis and Pontia Brassicæ the lobes are separated both before
and behind[25]; while in the larva of Dytiscus marginalis, but not in the
imago, in which there are two large hemispheres separated by a furrow, the
brain is undivided[26]. Cuvier mentions the larva of a saw-fly in which this
part is formed of four nearly equal spherical bulbs[27]: in the Scorpion (to
judge by the figure of Treviranus[28]) the two lobes represent an equilateral
triangle, the exterior angle of which terminates in several lesser spherical
bulbs; in Acrida viridissima, Nepa cinerea, Clubiona atrox, and the
common Louse, the lobes are pear-shaped[29].

ii. The spinal marrow and its ganglions[30]. From the posterior part of the
brain of insects, but in the ground and water beetles (Eutrechina and
Eunechina) from its sides below[31], issue two chords which diverging
embrace the œsophagus, and dipping below it and the intestines,—a
situation they maintain to the end of their course,—and in their further
progress uniting at intervals and dilating into several knots or ganglions,
compose their spinal marrow. This part is so named, from a supposed
analogy to the spinal marrow of vertebrate animals, which however admits
of some degree of doubt; yet, since it mixes the functions of that organ with
those of the great sympathetic nerves, the denomination is not wholly
improper, and may be retained. Though this chord is usually double when it
first proceeds from the brain, and surrounds the œsophagus like a collar, yet
in some insects it may be called a single chord. This is the case with that of
the common louse, in which Swammerdam could perceive no opening for
the transmission of the part just named[32]; if he was not mistaken in this,
the brain, as well as the rest of the spinal marrow in that animal, would be
below the intestines; from the figures of Treviranus it should seem that the
spiders, at least Clubiona atrox, are similarly circumstanced[33]; in the
cheese-maggot, which turns to a two-winged fly (Tyrophaga Casei), the
chord is also single, but it has a small orifice through which the gullet
passes[34]. At the union of the chords in other cases below that organ, a knot
or ganglion is usually formed, and an alternate succession of internodes and
ganglions commonly follows to the end. The internodes also may generally
be stated to consist of a double chord, though in many cases the two chords
unite and become one, or are distinguished only by a longitudinal furrow,
and even where they are really distinct and separable, in the body of the
insect they lie close together[35]. In the rhinoceros beetle (Oryctes
nasicornis) and Acrida viridissima &c. all the internodes consist of a
double chord[36]; but in many other insects numerous variations in this
respect occur.—Thus in the stag-beetle the last internode is single[37]; in the
caterpillar of the cabbage butterfly (Pontia Brassicæ) the five first are
double, and the six last single[38]; in that of the great goat-moth (Cossus
ligniperda) the three first only are double, but the others terminate in a
fork[39]; in the cockroaches (Blatta) the four first, in Hydrophilus piceus the
three first, and in Eristalis tenax the two first only are double, the rest being
all single[40]. A singular variation takes place in Hypogymna dispar; all the

internodes are single, except the second, the chords of which at first are
separate, and afterwards united[41]; and, to name no more, in Clubiona atrox
there is only one internode, which is single, with a longitudinal furrow[42].
In some, as in the louse, the grub of Oryctes nasicornis, and the cheese-
maggot, there are no internodes, the spinal marrow being formed of knots
separated only by slight or deep constrictions[43].

I must next say something of the ganglions[44]. Lyonet has observed that, in
the caterpillar of the great goat-moth, these in one respect differ remarkably
from the chords that connect them; in the latter the air-vessels or bronchiæ
only cover the outside of the tunic, while in the former they enter the
substance of the ganglion, which is quite filled with their delicate and
numberless branches[45]. Every ganglion may be regarded in some degree
as a centre of vitality or little brain[46], and in many cases, as well as the
brain, they are formed of two lobes[47]. I shall now consider them more
particularly as to their station, number, and shape.
1. With regard to the first head, their station, they are most commonly
divided between the trunk and abdomen; but in some cases, as in
Hydrophilus piceus and Acrida viridissima, the first ganglion is in the
head[48]; in others, as in the louse, the water-scorpion, and the grub of the
rhinoceros-beetle, they are confined to the trunk, their functions in the
abdomen being supplied by numerous radiating nerves[49]; in others again,
as in the scorpion, they are all abdominal. The ganglions vary also in their
situation with respect to each other. Thus in some, as in the larva of the
Chamæleon-fly (Stratyomis Chamæleon), they are so near as to appear like
a string of beads[50]; in that of the ant-lion (Myrmeleon) the two ganglions
of the trunk are separated by an interval from those of the abdomen, which
are so contiguous as to resemble the rattle of the rattle-snake[51]. In others
the internodes are longer, and the ganglions occur at nearly equal intervals,
as in the larva of the Ephemeræ[52]; but in the majority they are unequal in
length: thus in the scorpion the three first ganglions are the most distant[53];
in the hive-bee the third and fourth[54]; and in the spider the last[55].
2. The ganglions also in different species, and often in the same insect in its
different states, vary in their number. Thus in the grub of the rhinoceros-

beetle the whole spinal marrow appears like a single ganglion divided only
by transverse furrows[56]; in the water-scorpion there are two[57]; in the
louse there are three[58]; in the rhinoceros-beetle there are four[59]; five in
the stag-beetle[60]; seven in the hive-bee and some Lepidoptera[61]; eight in
the grub of the stag-beetle[62]; nine in the great Hydrophilus[63]; ten in
Dytiscus[64]; eleven in the grub of the great Hydrophilus[65]; twelve in the
grub of Dytiscus and the caterpillars of Lepidoptera[66]; thirteen in the larva
of Æshna[67]; and twenty-four in Scolopendra morsitans[68]. You must
observe that, generally speaking, the number of ganglions is less in the
imago than in the larva. With regard to the distribution of these knots to the
different primary parts of the body, the following table will exhibit it, as far
as I am acquainted with it, at one view. I omit those in which the ganglions
are only in one of these parts.
Head. Trunk. Abdomen.
Acrida viridissima 1 3 6[69]
Hydrophilus piceus 1 6 2
Clubiona atrox 0 2 1
Gryllotalpa vulgaris 0 2 7[70]
Myrmeleon, Larva 0 2 8[71]
Eristalis tenax 0 3 2[72]
Apis mellifica 0 3 4
Ephemera, Larva 0 3 7
Æshna, Larva 0 6 7
3. I am next to say a few words upon the shape of the ganglions. Most
commonly it approaches to a spherical figure, but in many instances, as I
said before, they, as well as the brain, consist of two lobes: they are,
however, seldom all precisely of the same shape. In the Dytisci, and Carabi,
the last is marked with a transverse furrow, which seems to indicate the
reunion of two[73]; in the stag-beetle, the first ganglion is oval or elliptical,
the second hexagonal; the third and fourth shaped like a crescent, and the
last like an olive[74]; in the caterpillar of the great goat-moth the first is
oblong and constricted in the middle, and the seven last are rhomboidal[75];
in the great Hydrophilus the second, and in the silk-worm all the ganglions

are quadrangular[76]; in Hypogymna dispar the third is heart-shaped[77]; the
great ganglion which forms the spinal marrow of the cheese-maggot is pear-
shaped[78]; that of the grub of the rhinoceros-beetle is fusiform[79]; and in
the scorpion all the ganglions are lenticular[80]. But the most remarkable in
this respect are those of a spider (Clubiona atrox): in this insect the brain
sits upon a bilobed ganglion of the ordinary form, which is immediately
followed without any internode by another bilobed one, terminating on each
side in four pear-shaped processes or fingers, which give it a very singular
appearance[81].

iii. The nerves[82] of insects, as of other animals, are white filaments
running from the brain and spinal marrow to every part of the body which
they are destined to animate; and their numerous ramifications, when
delineated, form no unpleasing picture[83]. In the caterpillar of the goat-
moth the accurate Lyonet counted forty-five pairs of them, and two single
ones, making in all ninety-two nerves; whereas in the human body
anatomists count only seventy-eight[84]. From the brain issue several pairs,
which go to the eyes, antennæ, palpi, and other parts of the mouth:
sometimes those that render to the mandibles issue from the first ganglion,
as in the larva of Dytiscus marginalis, the stag-beetle, &c.[85]; those both of
mandibles and palpi in the great Hydrophilus[86]; and in Blatta some which
act also upon the antennæ[87].
The optic are usually the most conspicuous and remarkable of the nerves. In
some insects with large eyes, as many Neuroptera, Hymenoptera, and
Diptera, their size is considerable; in the hive-bee they present the
appearance of a pair of kidney-shaped lobes, larger than the brain[88]; in the
dragon-flies, whose brain consists of two very minute lobes, these nerves
dilate into two large plates of a similar shape, which line all the inner
surface of the eyes[89]; in the stag-beetle they are pear-shaped, and
terminate in a bulb, from which issue an infinity of minute nerves[90]; it is
probable that this takes place in all cases, and that a separate nerve renders
to every separate lens in a compound eye[91]; the optic nerve in Dytiscus
and Carabus is pyramidal, with the base of the pyramid at the eye and the
summit at the brain[92]; in Eristalis tenax it is very large, cylindrical, and of
a diameter equal to the length of the last-mentioned part, upon the side of

which it is supported; it terminates in a very large bulb corresponding to the
eye[93]: in Scolopendra morsitans the optic nerves divide into four branches
long before they arrive at the eyes, and in this insect the nerves which
render to the antennæ are so thick as to appear portions of the brain, which
they equal in diameter[94]. Swammerdam discovered in the grub of the
rhinoceros-beetle and in the caterpillar of the silk-worm, a pair of nerves
which he regarded as analogous to the recurrent nerves in the human
subject, and therefore he distinguishes them by the same name[95]: they
issue from the lower surface of the brain, or that which rests on the
œsophagus, and at first go towards the mouth, but afterwards turn back, and
uniting form a small ganglion; this produces a single nerve, which passing
below the brain follows the œsophagus to the stomach, where it swells into
another ganglion, from which issue some small nerves that render to the
stomach, and one more considerable which accompanies the intestinal
canal, producing at intervals lateral filaments which lose themselves in the
tunics of that tube[96]. Lyonet afterwards discovered these nerves in the
caterpillar of the goat-moth[97], and Cuvier in other insects[98].
The other nerves which issue from the brain exhibit no remarkable features.
Those which originate in the spinal marrow are mostly derived from the
ganglions, and are sometimes interwoven with the muscles, as the woof
with the warp in a piece of cloth[99]; those from the three or four first
commonly rendering to the muscles of the legs, wings, and other parts of
the trunk, and those from the remainder to the abdomen. After their origin
they often divide and subdivide, and terminate in numerous ramifications
that connect every part of the body with the sensorium commune. A pair of
nerves is the most usual number that proceeds from each side of a
ganglion[100]; but this is by no means constant, since in the louse, the hive-
bee, and several other insects, only a single nerve thus proceeds[101]; and in
the larva of Ephemeræ, while two pairs issue from the six first ganglions,
only a single one is emitted by the five last[102]. In the spinal marrow of the
rhinoceros-beetle, both larva and imago, the nerves consist of simple
filaments which diverge like rays in all directions[103]: the same
circumstance distinguishes the cheese-maggot, only some of the nerves
appear to branch at the end[104]: in the louse, the last ganglion sends forth
posteriorly three pairs of nerves which render to the abdomen[105].

Sometimes, though rarely, nerves originate in the internodes of the spinal
marrow. Cuvier indeed has asserted that in invertebrate animals all the
nerves spring from the ganglions, and never immediately from the spinal
marrow; but Swammerdam, in describing those of the silk-worm, mentions
and figures four pairs as proceeding from the four anterior internodes,
excluding the first[106]; and at the same time he gives it as his opinion, that
all the nerves in insects really originate from the marrow itself, and not
from the ganglions, which he asserts are of a different substance, and are
inclosed in the marrow for the sake of giving it greater firmness[107]. In this
opinion, however, he seems singular[108]. Those remarkable nerves
described by Lyonet under the name of spinal bridle (bride épinière) also
take their origin, not from the ganglions, but from a bifurcation of the spinal
marrow. Of these, in the caterpillar of the goat-moth there are ten, the first
issuing from the bifurcation of the internode between the fourth and fifth
ganglions, and the remainder from the succeeding ones. After approaching
the succeeding ganglion, these nerves form a pair of branches that diverge
nearly at right angles from the bridle, and producing several lesser
branches, lose themselves in the sides of the animal[109]. Besides the nerves
above mentioned, two generally issue from the posterior part of the last
ganglion, diverging in opposite and oblique directions: some of these render
to the parts of generation; and in the silk-worm, and probably other species,
the innermost pair is perforated for the passage of the vasa deferentia[110].
After duly considering this general outline of the nervous system of insects,
the question will continually occur to you,—is then what you have called
the brain the sensorium commune of these animals, in the same manner as it
is in those with warm blood? To this query a negative must be returned. In
the latter, the brain is the common centre to which, by means of the nerves
and spinal marrow, all the sensations of the animal are conveyed, and in
which all its perceptions terminate. The nerves and spinal marrow are
merely the roads by which the sensations travel; and if their communication
with the brain, by any means be cut off at the neck, the whole trunk of the
animal becomes paralytic, evidently proving that the organ by which it feels
is the brain. This, however, is so far from being the case in insects, that in
them, if the head be cut off, the remainder of the body will continue to give
proofs of life and sensation longer than the head: both portions will live
after the separation, sometimes for a considerable period; but the largest

will survive the longest, and will move, walk, and occasionally even fly, at
first almost as actively without the head, as when united to it. Lyonet
informs us, that he has seen motion in the body of a wasp three days after it
had been separated from the head; and that a caterpillar even walked some
days after that operation; and when touched, the headless animal made the
same movements as when intire[111]. Dr. Shaw has observed—an
observation confirmed in Unzer's Kleine Schriften,—that if Geophilus
electricus be cut in two, the halves will live and appear vigorous even for a
fortnight afterwards; and what is more remarkable, that the tail part always
survives the head two or three days[112]. The sensorium commune of
insects, therefore, does not, as in the warm-blooded animals, reside in the
brain alone, but in the spinal marrow also. It was on this account probably
that Linné denied the existence of a brain in insects, regarding it merely as
the first ganglion of the spine.
Cuvier and other modern physiologists, from the ganglionic structure of this
organ, are of opinion that it is not the analogue of the cerebro-spinal system
of vertebrate animals, but rather of their great sympathetic nerves. Indeed,
considering solely the external structure of the nervous system of insects, a
great resemblance strikes us between it and these nerves; for besides its
general ganglionic structure, there is also in them an upper ganglion in the
neck, seemingly corresponding with what we have named the brain of
insects, from which the nervous chord dips to the lower part of the neck,
where it forms a second ganglion, which appears to correspond with what
we have considered as their second ganglion[113]. We may observe,
however, that at least in one respect there is even an external resemblance
between the brain of insects and that of vertebrate animals:—it most
commonly consists, as has been stated, like them, of two lobes, often very
distinct; a circumstance which not unfrequently distinguishes the other
ganglions[114], and is not borrowed from the ganglions of the great
sympathetics. With respect to the internal structure of the ganglions and
spinal marrow of insects, we know little to build any theory upon, except
that the internal substance of the former is filled with air-vessels; at least so
Lyonet, as has been already observed, found in the goat-moth, while only
the tunics of the latter are covered by them. Taking the above resemblance
to the brain of vertebrates into consideration, there appears ground for
thinking that the nervous system of insects, like some of their

articulations[115], is of a mixed kind, combining in it both the cerebro-spinal
and the ganglionic systems; and this will appear further if we consider its
functions.
That learned and acute physiologist Dr. Virey, assuming as an hypothesis,
that the structure of the system in question is simply ganglionic, and merely
analogous to the sympathetic system of vertebrate animals, has built a
theory upon the assumption, which appears evidently contradicted by facts.
Because, as he conceives after Cuvier, insects are not gifted with a real
brain and spinal marrow, he would make it a necessary consequence that
they have no degree of intellect, no memory, judgement or free will; but are
guided in every respect by instinct and spontaneous impulses,—that they
are incapable of instruction, and can superadd no acquired habits to those
which are instinctive and inbred[116]. This consequence would certainly
necessarily follow, was their nervous system perfectly analogous to the
sympathetic of warm-blooded animals. But when we come to take into
consideration the functions that in insects this system confessedly
discharges, we are led to doubt very strongly the correctness of the
assumption. Now in these animals the system in question not only renders
to the nutritive and reproductive organs, which is the principal function of
the great sympathetic nerves in the vertebrates; but by the common organs
maintains a connexion with the external world, and acquires ideas of things
without, which in them is a function of the cerebral system: from the same
centre also issue those powers which at the bidding of the will put the limbs
in action, which also belongs to the cerebral system. That insects have
memory, and consequently a real brain, has been before largely proved, as
also that they have that degree of intellect and judgement which enables
them to profit by the notices furnished by their senses[117]. What can be the
use of eyes,—of the senses of hearing, smelling, feeling, &c. if they are not
instructed by them what to choose and what to avoid? And if they are thus
instructed—they must have sufficient intellect to apprehend it, and a portion
of free will to enable them to act according to it. With regard to the
assertion that they are incapable of instruction, or of acquiring new habits;
few or no experiments have been tried with the express purpose of
ascertaining this point: but some well-authenticated facts are related, from
which it seems to result that insects may be taught some things, and acquire
habits not instinctive. They could scarcely be brought from their wild state,

and domesticated, as bees have been so universally, and both ants and
wasps occasionally[118], without some departure from the habits of their
wild state; and the fact of the corsair-bees, that acquire predatory habits
before described[119], shows this more evidently: but one of the most
remarkable stories to our purpose upon record, is that of M. Pelisson, who,
when he was confined in the Bastile, tamed a spider, and taught it to come
for food at the sound of an instrument. A manufacturer also in Paris, fed 800
spiders in an apartment, which became so tame that whenever he entered it,
which he usually did bringing a dish filled with flies but not always, they
immediately came down to him to receive their food[120].
All these circumstances having their due consideration and weight, it
seems, I think, most probable, that as insects have their communication
with the external world by means of certain organs in connexion with their
nervous system, and appear to have some degree of intellect, memory, and
free will, all of which in the higher animals are functions of a cerebral
system, and at the same time in other respects manifest those which are
peculiar to the sympathetic system,—it is most probable, I say, as was
above hinted, that in their system both are united.
I must bespeak your attention to a circumstance connected with the subject
of this letter, which merits particular consideration: I mean the gradual
change that takes place in the nervous system when insects undergo their
metamorphoses; so that, except in the Orthoptera, Hemiptera, and
Neuroptera Orders, in which no change is undergone, the number of
ganglions of the spinal chord is less in the imago than in the larva. There
seems an exception indeed to this rule in the case of the rhinoceros-beetle,
in the larva of which there is only one ganglion, while in the imago there
are four[121]. But as this one ganglion occupies the whole spinal marrow, it
is really of greater extent than the four of the imago; so that even in this
case there is a concentration of the cerebral pulp. In some cases, as in
Dytiscus marginalis, and Hydrophilus piceus[122], the imago has only one
ganglion less than the larva, but more generally it loses four or five. Dr.
Herold has traced the gradual changes that take place in the spinal marrow
of the common cabbage-butterfly (Pontia Brassicæ), from the time that it
has attained its full size to its assumption of the imago. Of these I shall now
give you some account.

In the full-grown caterpillar, besides the brain there are eleven ganglions,
the chords of the four first internodes being double, and the rest single:
from each ganglion proceed two pairs of nerves, one from each side. In this
the lobes of the brain form an angle with each other[123]. In two days the
double chords mutually recede, so as to diminish the interval between the
ganglions, and the single ones have become curved: thus the length of the
spinal marrow is shortened about a fourth, and the fourth and fifth
ganglions have made an approach to each other[124]. On the eighth day,
when the insect has assumed the pupa but remains still in the skin of the
caterpillar, the flexure of the internodes is much increased; the first
ganglion is now united to the brain, and the fourth and fifth have joined
each other, though they are still distinct; the spinal marrow has now lost
considerably more than a third of its length[125]. On the fourteenth day, the
internodes, except the double ones, have become nearly straight again; the
fourth and fifth ganglions have coalesced so as to form one, and the sixth
and seventh have each lost their pairs of nerves[126]. Shortly after this, these
last ganglions have nearly disappeared, and the chords of the three first
internodes have again approached each other[127]. The next change
exhibited is the absorption of the first ganglion by the brain, the union of
the chords of the first internode, which is now straight, the approximation
of the second and third ganglions, and the enlargement of the one formed by
the union of the fourth and fifth, at the expense perhaps of the sixth and
seventh, which have now intirely disappeared, and in their place is a very
long internode. These united ganglions retain the pairs of nerves they had
when separate[128]. Just before the assumption of the imago, the direction of
the lobes of the brain becomes horizontal, the second and third ganglions
unite, and the internode between the third and fourth is shortened[129].
Lastly, when the animal is become a butterfly, the second and third
ganglions have coalesced, and are joined to that formed by the union of the
fourth and fifth; a short isthmus or rather constriction, with an orifice, being
their only separation: each of these united ganglions send forth laterally
four pairs of nerves[130]. In his figure, Dr. Herold has not represented the
orifice for the passage of the gullet, but doubtless one exists, which for an
animal that imbibes only fluid food is probably very minute. In Hypogymna
dispar, we learn from Cuvier, this orifice is of that description, and of a
triangular shape[131].

It can admit of no reasonable doubt that one of the principal intentions of
these changes is to accommodate the nervous system to the altered
functions of the animal in its new stage of existence, in which the antennæ,
eyes, and other organs of the senses, as well as the limbs and muscles
moving them, and the sexual organs, being very different from those of the
larva, and if not wholly new, yet expanded from minute germs to their full
size, may well demand corresponding changes in the structure of the
nervous system by which they are acted upon.
But are these changes also concerned, as Dr. Virey conjectures, in
producing that remarkable alteration which usually takes place between the
instincts of the larva and imago? In order to answer this question, it will be
requisite first to quote the ingenious illustration with which this able
physiologist elucidates his ideas on this point. "The more readily," he
observes, "to comprehend the action of instinct, let us compare the insect to
one of those hand-organs in which a revolving cylinder presents different
tunes noted at its surface, and pressing the keys of the pipes of the organ,
gives birth to all the tones of a song: if the tune is to be changed, the
cylinder must be pulled out or pushed in one or more notches, to present
other notes to the keys. In the same manner let us suppose that nature has
impressed or engraved certain determinations or notes of action, fixed in a
determinate series in the nervous system and the ganglions of the
caterpillar, by which alone she lives, she will act according to a certain
sequence of operations; and, so to speak, she will sing the air engraven
within her. When she undergoes her metamorphosis into a butterfly, her
nervous system being, if I may so express myself, pulled out a notch, like
the cylinder, will present the notes of another tune, another series of
instinctive operations; and the animal will even find itself as perfectly
instructed and as capable of employing its new organs, as it was to use the
old ones. The relations will be the same; it will always be the play of the
instrument[132]."
This illustration is doubtless at the first glance very striking and plausible:
but a closer examination will, I think, show, that, as in so many other
instances in metaphysical reasoning, when fanciful analogies are substituted
for a rigid adherence to stubborn facts, it is satisfactory only on a superficial
view, and will not stand the test of investigation; and as this is a question
intimately connected with what I have advanced on the subject of instinct in

a former letter, I must be permitted to go somewhat into detail in
considering it.
To prove his position, Dr. Virey ought at least to be able to show that,
whenever a change takes place in the instincts of insects in their different
states of larva and imago, a corresponding change takes place in the
external structure of the nervous chord. But what are the facts? In three
whole orders, viz. Orthoptera Hemiptera, and Neuroptera, as mentioned
above[133], the structure of the nervous chord is not changed; and yet we
know that many tribes of these orders acquire instincts in their imago state
altogether different from those which directed them in their state of larvæ.
A perfect Locust, for instance, acquires the new instincts of using its wings;
of undertaking those distant migrations of which so many remarkable
instances were laid before you in a former letter[134]; and, if a female, of
depositing its eggs in an appropriate situation. But if such striking changes
in the instinct of these tribes can be effected without any perceptible
alteration in the structure of the nervous chord, it is contrary to the received
rules of philosophical induction to refer to this alteration the changes in the
instincts of other tribes where it is found. Is it not far more probable that
this alteration has in fact no connexion with the changes of instinct, but is
solely concerned with those remarkable changes in the organs of sense and
motion, which occur in the larva and imago states of the orders in which it
is observed? In a common caterpillar, the form of the body, the legs, the
eyes, and other organs of the senses, all strikingly differ from those of the
imago; whereas, with the exception of the acquisition of new wings, a
perfect locust differs little from its larva: so that we may reasonably expect
a corresponding change, such as we find it, in the structure of the nervous
chord of the lepidopterous insect, not called for in that of the neuropterous
species, in which accordingly it does not take place.
This reasoning, in opposition to Dr. Virey's theory, that the changes of
instinct depend on the altered structure of the nervous system, becomes
greatly strengthened when we advert to the higher classes of animals, which
surely in any investigation of the nature of instinct ought to be closely kept
in view; for the faculty, though often less perfect in them than in insects, is
still of the same kind, and may consequently be expected to follow the same
general laws. In a young swallow, for example, all its instincts are not
developed at once any more than in an insect. The instinct which leads it to

migrate does not appear for some months after its birth, and that of building
a nest still later. But we have not the slightest ground for believing that
these new instincts are preceded by any change in the structure of the great
sympathetic nerve, or of any other portion of the nervous system: and the
same may be said as to the sexual instincts developed in quadrupeds some
years subsequent to their birth. If, then, these remarkable changes in the
instinct of the higher classes of animals can take place independently of any
visible change in the nerves, what substantial reason can be assigned why
they may not also in the class of insects?
On the whole, I think you will agree with me, that there is nothing in Dr.
Virey's hypothesis which should lead me to alter the opinion I have already
so strongly expressed in a former letter[135], as to the insufficiency of the
mechanical theories of instinct hitherto promulgated, adequately to explain
all the phenomena; and unless they do this they are evidently of small
value. Such theories as I have there adverted to may often seem to be
supported by a few insulated facts, but with others, far more numerous, they
are utterly at variance; and, to omit many other instances, I am strongly
inclined to doubt the possibility of satisfactorily explaining the variety of
instincts exercised by a bee[136], or the extraordinary development of new
ones in particular circumstances only[137], on any merely mechanical
grounds.
And after all, even suppose it could be demonstratively shown that every
instinct is as clearly dependent on secondary causes, as I have formerly
admitted that some doubtless seem to be, yet what would this teach us as to
the essential nature of instinct? We have advanced indeed a step; but still, as
I have before observed in referring to the theories of Brown and Tucker, we
have only placed the world upon the tortoise, and instinct, as to its essence,
which is what we want to detect, is as mysterious as ever: just as, though we
can clearly prove that the mind is acted upon by the senses, yet this throws
no light upon the essential nature of the mind, which we are forced to admit
is inscrutable, as if to teach us humility, and prevent our vainly fancying,
that though allowed to discover some of the arcana of nature, we shall ever
be able to penetrate into her inmost sanctuaries.
That Dr. Virey should regard instinct in insects as purely mechanical was
the natural consequence of his denying them any portion of intellect; but his

opinion cannot I think be consistently assented to, if it be the fact, as I have
just shown[138], that they are not wholly devoid of the intellectual principle.
Whatever is merely mechanical, must, under similar circumstances, always
act precisely in the same way. An automaton once constructed, whilst its
machinery remains in order, will invariably perform the same actions; and
Des Cartes, when he had constructed his celebrated female automaton,
imagined that he had irrefragably proved his principle, that brutes are mere
machines. But if, instead of losing himself in the wilds of metaphysical
speculation, he had soberly attended to facts, he would have seen that the
instinct of animals can be modified and counteracted by their intellect, and
consequently cannot be regarded as simply mechanical. Though the
instinctive impulse of an empty stomach powerfully impel a dog to gratify
his appetite, yet, if he be well tutored, the fear of correction will make him
abstain from the most tempting dainties: and in like manner a bee will quit
the nectary of a flower, however amply replenished with sweets, if alarmed
by any interruption. The ants on which Buonaparte amused himself with
experiments at St. Helena, though they stormed his sugar-basin when
defended by a fosse of water, controlled their instinct and desisted when it
was surrounded with vinegar[139]: and in the remarkable instance
communicated to Dr. Leach by Sir Joseph Banks, the instinct of a crippled
spider so completely changed, that from a sedentary web-weaver it became
a hunter[140]. There is evidently, therefore, no analogy between actions
strictly mechanical and instincts, which, though they may often seem to be
excited by mechanical causes, are liable to be restrained or modified by the
connexion of the instinctive and intellectual faculties[141]; and while we are
ignorant how this connexion takes place, it is obviously impossible to
reason logically on the subject.
In thus denying that any existing mechanical theory of instinct is
satisfactory, I by no means intend to assert that instinct is purely
intellectual. I have already given you my opinion[142], that it is not the
effect of any immediate agency of the Deity; nor am I prepared to assent to
the doctrine of a writer, who has in some respects written ably on the
subject in question, who says, that "the Divine Energy does in reality act not
immediately, but mediately, or through the medium of moral and
intellectual influences upon the nature or consciousness of the creature, in
the production of the various, and in many instances truly wonderful,

actions which they perform[143]." The same objection applies to this as to so
many other metaphysical theories, that it is not adequately supported by
facts; and all theories not so supported are injurious to science in proportion
as their plausibility is greater, by leading the student to relax in that
observation of nature and attentive study of the instincts of animals, on
which alone sound hypothesis on this subject can be ultimately founded.
I shall conclude these remarks on the nature of instinct with a few
observations as to the circumstances in which insects may be supposed to
be guided by this faculty, and those in which intellect seems to direct them.
The bee, when it takes its flight to a field where flowers abound, is
governed by intellect in the use of its senses; for these are given to it as
guides: and when it arrives there, they direct it to the flowers, and enable it
to ascertain which contains the treasures it is in search of; but having made
this discovery, its instinct teaches it to imbibe the nectar and load its hind
legs with pollen.—Again: its senses, aided by memory, enable it to retrace
its way to the hive, where instinct once more impels it in its various
operations. So that when we ascribe a certain degree of intellect to these
animals, we do not place them upon a par with man; since all the most
wonderful parts of their economy, and those manipulations that exceed all
our powers, we admit not to be the contrivance of the animals themselves,
but the necessary results of faculties implanted in their constitution at the
first creation by their Maker. I may further repeat, that the mere fact of
being endowed with the external organs of sense, proves a certain degree of
intellect in insects. For if in all their actions they were directed merely by
their instinct, they might do as well without sight, hearing, smell, touch, &c.
but having these senses and their organs, it seems to me a necessary
consequence, that they must have a sufficient degree of intellect, memory,
and judgement, to enable them advantageously to employ them.
There is this difference between intellect in man, and the rest of the animal
creation. Their intellect teaches them to follow the lead of their senses, and
make such use of the external world as their appetites or instincts incline
them to,—and this is their wisdom; while the intellect of man, being
associated with an immortal principle, and being in connexion with a world
above that which his senses reveal to him, can, by aid derived from heaven,
control those senses, and bring under his instinctive appetites, so as to

render them obedient to the το ἡγεμονικον, or governing power of his
nature: and this is his wisdom.
I am, &c.

LETTER XXXVIII.
INTERNAL ANATOMY AND PHYSIOLOGY OF INSECTS
CONTINUED.
RESPIRATION.

"Life and flame have this in common," says Cuvier, "that neither the one
nor the other can subsist without air; all living beings, from man to the most
minute vegetable, perish when they are utterly deprived of that fluid[144]."
The ancients, however, not perceiving insects to be furnished with any thing
resembling lungs, took it for granted that they did not breathe; though Pliny
seems to hesitate on the subject[145]. But the microscopic and anatomical
observations of Malpighi, Swammerdam and Lyonet, and the experiments
of more modern physiologists, have incontestably proved that insects are
provided with respiratory organs, and that the respiration of air is as
necessary to them as to other animals. They can exist indeed for a time in
irrespirable air; and immersion in hydrogen or carbonic acid gases is not, as
I have often ascertained, so instantly fatal to them as it would be to
vertebrate animals; but like them, they speedily perish in air altogether
deprived of its oxygen, or placed in situations to which all access to this
essential element is excluded. Their respiration too of atmospheric air
produces the same change in it with that of the vertebrate animals, the
oxygen disappearing, and carbonic acid gas being produced in its place.
Boyle had long since ascertained, that when bees, flies, and other insects
were placed under an exhausted receiver, they often perished[146]: and the
same effect was even observed by the ancients to ensue, when their bodies
were by any means covered with oil or grease, which necessarily closed the
orifices of their respiratory organs[147].
But for the first series of experiments ascertaining the necessity of a supply
of air to insects, and their conversion of it into carbonic acid, we are
indebted to the illustrious Scheele[148]; and his experiments have been
repeated and confirmed by Spallanzani, Vauquelin, and other chemists. The

former found, that when caterpillars and maggots were confined in vessels
containing only about eleven cubic inches of atmospheric air, though
furnished with sufficient food, they soon died, and sooner when the space
was more confined[149]. He ascertained too, that a larva weighing only a
few grains consumed, in a given time, as much oxygen as an amphibious
animal a thousand times as voluminous[150]. A male grasshopper (Acrida
viridissima) in six cubic inches of oxygen lived but eighteen hours, and the
female placed in eight cubic inches of atmospheric air, only thirty-six hours.
The usual tests in both instances detected the conversion of the oxygen
present into carbonic acid[151]. Precisely the same result was obtained by
Sorg and Ellis, who, having placed a number of flies in nine cubic inches of
atmospheric air, found them all dead by the third day, the oxygen intirely
vanished, and a quantity of carbonic acid nearly equal in bulk produced[152].
It is ascertained too, that insects like other animals require in the process of
respiration not merely oxygen, but such a mixture of it with nitrogen or
azote as composes atmospheric air: for Vauquelin found that a grasshopper
placed in six cubic inches of oxygen lived only half as long (eighteen hours)
as another placed in eight inches of atmospheric air; its breathing was much
more laborious, and it died when not more than one-twentieth of the oxygen
had been converted into carbonic acid[153]. That a large quantity of oxygen
penetrates all parts of insects, is evident also from the acid prevalent in the
fluids of most of them, as likewise from the wonderful power of their
muscles. That azote is also received, seems probable from the ammonia
which has been extracted from the fluids of many, and from the rapid
putrescence of these animals[154].
The mode, however, in which the respiration of insects is carried on, differs
greatly from that which obtains in the higher animals. They have no lungs,
no organs confined to a particular part of the body, by means of which the
whole of the blood is regularly exposed to the action of the inspired air.
They do not breathe through the mouth, but through numerous orifices
called spiracles, and the respiratory vessels connected with these are
conducted to every part of the body. In some indeed, that we have included
under the denomination of insects, as the Arachnida, an approach is made
to the branchial respiration of fishes.

The respiratory apparatus of insects may be considered under two principal
heads:—viz. the orifices or spiracles, and other external organs by which
the air is alternately received and expelled; and the internal ones, by which
it is distributed. Each of these is well worthy of your attention.
I. The external respiratory organs of insects may be divided into three
kinds. Spiracles; Respiratory plates; and branchiform and other pneumatic
appendages.

i. Spiracles[155] (Spiracula), or breathing pores, are small orifices in the
trunk or abdomen of insects, opening into the tracheæ, by which the air
enters the body, or is expelled from it[156]. They may be considered
principally as to their composition and substance; shape; colour;
magnitude; situation; and number.
1. Composition and substance. Perhaps you may not be aware that the
structure of these minute apertures is not so simple as at the first view it
may seem; but when you recollect that by them the insect breathes, you will
suspect that provision may be made for their opening and shutting. A
spiracle therefore, speaking analogically, may be regarded in numerous
cases as a mouth closed by lips. In caterpillars and many other insects, the
substance of the crust where it surrounds the spiracle, is elevated so as to
form a ring round it. The lips, properly speaking, are formed of a single
cartilaginous piece or platform, with a central longitudinal cleft or opening,
when closed often extending the whole length of the piece[157]; but in some
appearing always open and circular: of the former description are those
covered by the elytra in the common cockchafer; and of the latter, those that
are not so covered: in some, as in the antepectoral pair of the mole-cricket,
there appear to be no lips, the orifice being merely closed with hairs[158].
Though the aperture is usually in the middle of the platform, in the female
of Dytiscus marginalis, it is nearer the posterior side, the anterior or upper
lip being the longest. In the majority, the mouth or cleft is nearly as long as
the spiracle; yet in the puss-moth (Cerura Vinula) it is shorter[159]. Some
spiracles, however, are unilabiate, or have only one lip. This is the case with
Gonyleptes and perhaps others[160]. The lips are usually horizontal, but
sometimes they dip so as to make the spiracle appear open.

With regard to the substance of these organs, it is more or less cartilaginous,
and probably elastic; the surface frequently appears to be corrugate or
plaited; this is very distinctly seen in the stag-beetle and the cockchafer: in
the last insect, under a powerful magnifier, we are told that the lips appear
to consist of parallel cartilaginous processes, separated by a cellular
web[161]. In some species of Copris the corrugations form a perplexed
labyrinth; in the caterpillar of the puss-moth the plaits are so narrow as to
look like rays[162]; and in some Dynastidæ the lips approach to a lamellated
structure. Again, in Hydrophilus caraboides the upper lip, and in Dytiscus
circumflexus, both lips seem formed of elegant plumes[163]: a similar
ornament distinguishes the inner edge of the lips in the caterpillar of the
great goat-moth (Cossus ligniperda) and others[164]. In the grub of the
rhinoceros-beetle (Oryctes nasicornis) the margin of the lower or inner lip
is decorated by pinnated rays, which enter the cellular membrane that
covers the upper lip[165]: in this larva, and that likewise of the cockchafer,
the two lips are formed of different substances; in the last the upper or outer
one consists of a perforated cellular membrane, through which the air can
pass, while the lower or inner one is a cartilaginous valve that closes the
orifice[166]: in the former this valve is surmounted by a boss[167]. In the
pupa of Smerinthus Populi, a hawk-moth not uncommon, and of some
dragon-flies (Libellula depressa), the margin of the two lips is crenated,
probably with notches which alternate, that the mouth of the spiracle may
shut more accurately[168]. The substance is unusually thick in the spinose
caterpillars of butterflies; and in the pupa of one, Uria Proteus, it is villose.
Under the present head I may observe, that in some cases, as in the puss-
moth, and the larva of the common water-beetle (Dytiscus marginalis), the
spiracles are closed by a semifluid substance, which however, according to
Sprengel, is permeable to the air[169]. The animal, where these organs are
furnished with lips, has doubtless, by means of a muscular apparatus, the
power of opening and shutting them: this is done, we are told, by elevating
and depressing, or rather by contracting and relaxing them. Sorg counted in
one case (Oryctes nasicornis) twenty, and in another (Acrida viridissima)
fifty, of these motions to take place in little more than two minutes[170]: but
the quickness and force of this motion is not always uniform; for the same
physiologist observed, that in Carabus auratus, when feeding or moving its

body rapidly, the contraction of the spiracles took place at very short
intervals; but when it was fasting, and its motions were slow, the intervals
were longer[171]: it is probable also, that the temperature may accelerate or
retard the motion. In the summer I examined a specimen of Phyllopertha
horticola, that had indeed been somewhat injured, with this view: the pulses
of the abdomen, which alternately rose and fell, were at about the rate of the
pulse of a man in health, sixty in a minute, and the spiracles appeared to me
to keep pace with this motion: later in the year, when the temperature was
lower, as I was walking, I took a specimen of some grasshopper (Locusta).
Upon viewing it under a lens, I observed one of the convex pectoral
spiracles open and shut, and the interval between two breathings appeared
nearly half a minute.
2. With regard to their shape, spiracles vary considerably. In general we
may observe that the abdominal ones are usually flat, while those of the
trunk are often convex[172]. Sometimes they are very narrow and nearly
linear, as in many pupæ of Lepidoptera, and those in the metathorax of the
sand-wasps (Ammophila) and affinities; at others they are wider and nearly
elliptical, as in Lucanus and many Lamellicorn beetles: again, in Copris
they are circular; in Cordylia Palmarum ovate; in Dytiscus oblong[173]; in
Goerius olens lunulate; in Gonyleptes nearly of the shape of a horse-
shoe[174]; and probably many other forms might be traced, if a thorough
investigation with this view were undertaken.
3. The colour of spiracles will not detain us long. In the caterpillars of
Lepidoptera this is often so contrasted with that of the rest of the body, as to
produce a striking and pleasing effect. Thus when the body is of a dark
colour, they are usually of a pale one[175]; or if the body is pale, they are
dark[176], or surrounded with a dark ring[177]. This contrast is often rendered
more striking by their position with regard to the partial colours that often
ornament caterpillars: in those whose sides are decorated by a longitudinal
stripe, the spiracles are often planted in it[178]; or just above it[179]; or
between two[180]: in some hawkmoths the intermediate ones are set in white
or pale spots, which gives great life to the appearance of the animal. In
general, in perfect insects the most prevalent colour is buff, or reddish-
yellow. In the larva of the great water-beetle these organs resemble the iris

of the eye, being circular with concentric rings alternately pale and
dark[181].
4. The size of spiracles varies considerably. Those in the larva last
mentioned are so minute as to be scarcely visible except under a lens, while
those behind the fore-legs in the mole-cricket are a full line in length, and
those in the pleura of Acrocinus accentifer, a Brazilian Capricorn beetle,
are more than twice as long. In the same species they are often found of
different sizes;—thus the anal pairs in the water-beetle lately alluded to, I
mean in the perfect insect, are much larger than the rest[182], probably that
the animal may imbibe a larger quantity of air when it rises to the surface of
the water, where it suspends itself by the tail. In those Lamellicorn beetles
in which the terminal part of the abdomen is not protected by the elytra, the
covered spiracles are the largest.
5. Under the next head, the situation of spiracles, I shall not only consider
the part of the body in which they are situated, but likewise their position in
the crust; to which last, as it will not detain us long, I shall first call your
attention. Their position in this respect is most commonly oblique: but in
the abdomen of the above water-beetle they are transverse, and in a larva I
possess, probably of an Elater, they are longitudinal. In spinose caterpillars
these organs are generally planted between two spines, one being above and
the other below. The lateral line of the body most commonly marks their
situation; but in many cases they become ventral, and in others dorsal. The
most important circumstance, however, connected with the present head is
their appropriation to particular segments or parts of the body, for, like the
ganglions of the spinal marrow, they are distributed to almost every
segment. Let us take a summary view of their arrangement in this respect.
No insect has any spiracle in the head; but in caterpillars and many other
larvæ there is a pair in the first segment of the trunk. This is also to be
found in the other states, but is not easily detected in the pupæ of
Lepidoptera: in the Coleoptera order, in the grub of the Lamellicorn
beetles, it is extremely conspicuous, and planted in the side of the first
segment[183]; in other Coleopterous grubs it is not so readily found, but
probably its station is somewhere behind the base of the arms, where it is
very visible in that of the Staphylinidæ. In the imago of insects of this order,
this antepectoral spiracle has been overlooked, and indeed is not soon

discovered: to see it clearly, the manitrunk should be separated from the
alitrunk; and then if you examine the lower side of the cavity, you will see a
pair of, usually, large spiracles planted just above the arms, in the ligament
that unites these two parts of the trunk to each other: in the common rove-
beetle, however, (Goerius olens)you may easily see it without
dissection[184]. In the Orthoptera it is situated behind the arms, as in
Gryllotalpa: or between them and the prothorax, as in Blatta: in the
Hemiptera and Neuroptera probably the situation is not very different. In
the Lepidoptera this pair of spiracles is planted just before the base of the
upper or primary wings[185]: a similar situation, I suspect, is appropriated to
it in the Trichoptera, but covered by a tubercle or scale. Something similar
has been noticed by M. Chabrier, in the same situation and circumstances,
in the collar of Hymenoptera[186]. In numerous Diptera this breathing pore
is planted on each side between the collar and the dorsolum above the
arms[187], and in Hippobosca in the collar itself[188].
In Lepidopterous, Coleopterous, and some other larvæ, the two segments of
the body corresponding with the alitrunk in the perfect insect, are without
spiracles, neither have they in this state, though pneumatic organs have
been discovered[189], any real ones in that part: but not so the remaining
orders, all of which have these organs in that section of the trunk. To begin
with the Orthoptera:—in Blatta there seems to be a long narrow one behind
the intermediate leg; in the Gryllotalpa there is one in the posterior part of
the pleura; and in Locusta, above both the intermediate and hind legs[190]. It
is probable, that in general those that have no spiracles in the manitrunk
have four in the alitrunk, which seems the natural number belonging to the
trunk. In many of the Heteropterous Hemiptera in the parapleura there is an
open spiracle without lips[191], to which, as in that beautiful bug Scutellera
Stockeri, a channel sometimes leads. The space in which this spiracle is
planted in other genera of bugs (Pentatoma &c.) is covered with a kind of
membranous skin, often much corrugated[192]. In the aquatic insects of this
section, and many terrestrial ones, as Reduvius, &c. this spiracle is obsolete.
There is another circumstance, possibly connected with their respiration,
relating to many of the bugs, which may be mentioned here. If you examine
Pentatoma rufipes, a very common one, you will find between the scapula
and parapleura a long orifice or chink; this upon a closer inspection, under

a good magnifier, you will see completely filled with minute stiff hairs or
bristles, which fringe the posterior margin of the scapula[193]. In a Brazilian
species of Lygæus (sexmaculatus K. M. S.) with incrassated posterior
thighs, these hairs are replaced by lamellæ which have the aspect of gills. A
red, vertical, convex spiracle, with its orifice towards the head, and
terminating posteriorly in a kind of conical sac, is situated towards the
hinder part of the pleura in the giant water-scorpion (Belostoma
grandis[194]); this seems analogous to one lately mentioned in the mole
cricket. In the other section of this Order it is not easy to decipher the parts
of the under side of the alitrunk. In Fulgora, Cicada, and many others of its
genera, there appears to be more than one opening into the chest; but
whether they are of a pneumatic nature or not, can only be ascertained by an
inspection of the living animal. There is a very visible spiracle over each of
the four last legs of the Libellulina[195], but in the remainder of the
Neuroptera Order they have eluded my search. In the Hymenoptera and
Diptera they are nearly in the same situation, being placed behind the wings
on each side of the metathorax; in the latter Order with the poiser near them
on the inner side[196]: in this also, the spiracles of the trunk are without lips,
except in the larvæ, but are often merely an orifice, sometimes fringed with
hairs; this is particularly conspicuous in Syrphus, in which these orifices are
very large, and in some species closed by an elegant double fringe of white
hairs. This is doubtless to prevent the entrance of any particles of dust or the
like.
We are next to consider the situation of the spiracles of the abdomen: these
which are supposed to be appropriated exclusively to inspiration, are
usually more numerous than those of the trunk, by which it is probable that
expiration is performed, and have principally attracted the notice of
Entomologists: they are either dorsal, lateral, or ventral. In Dytiscus,
Copris, &c. amongst the beetles, all the spiracles are dorsal; in the larvæ of
Coleoptera and Lepidoptera they are lateral; and in the Heteropterous
Hemiptera they are usually ventral: in Dynastes they are commonly found
of all three descriptions;—the three first being dorsal, the two next lateral,
and the last pair ventral[197]. In some instances, as in Perga Kirbii, and
probably other Hymenoptera, these organs are planted in that portion of the
dorsal segment which turns under, as was observed in a former letter[198],
and becomes ventral. Generally there is a pair of spiracles to each segment,

and in those insects that have a hypochondriack joint[199] there is often a
spiracle in it. The last segment of the abdomen is always without these
orifices, as is the basal one in Velia, Ranatra, and some other bugs. A
singular anomaly distinguishes the Libellulina: they appear to have no
abdominal spiracles[200], yet I have seen the abdomen of Libellula depressa
when reposing, contract and dilate alternately, from whence it follows that
this part is concerned in respiration. Sprengel says that the larvæ in this
tribe have seven or nine on each side[201], and Reaumur speaks of them as
discoverable in the pupa[202]. I have carefully examined the pupa-skin of
most of the genera of Libellulina, under a powerful magnifier, but have not
succeeded in discovering any thing like these organs in the abdomen. The
Ephemera and probably the other Neuroptera have abdominal spiracles[203].
M. Latreille observed one on each side of the base of the scale on the
footstalk of the abdomen in ants[204]. Generally the abdominal spiracles
may be described as planted in the crust of the insect; but in many cases
their station is in the membranous folds, which I have therefore named the
pulmonarium, that sometimes separate the dorsal from the ventral
segments: these folds allow of a considerable distention of the abdomen,
which is probably necessary when all the air-vessels are full. In a gravid
Ichneumon I once saw it enlarged to more than twice its natural size by
means of this membrane, through which the eggs were distinctly visible.—
Before I bid adieu to this subject, I must say a few words upon the situation
of the organs in question in the myriapods. In Iulus, in each segment is a
pair of orifices which have usually been regarded as spiracles, but M. Savi
found that these orifices opened into vesicles containing a fetid fluid, and
upon a very close examination he discovered the real spiracles above the
base of the legs, in connexion with tracheæ[205]. In some of the larger
species of Scolopendræ large open spiracles in the same situation are
extremely visible[206]. Cermatia presents a singular anomaly:—a single
series of spiracles of the usual form, each planted in a cleft of the posterior
margin of the dorsal scuta, runs along the back of the animal[207]: unless we
may suppose that, like the seeming spiracles of Iulus just mentioned, these
are merely orifices by which it covers itself with some secretion.
6. A few words upon the number of spiracles.—If you examine the common
dog-tick (Ixodes Ricinus), you will find only one of these organs on each

side of the abdomen[208]; the Libellulina, as we have seen, have only four,
all in the trunk; in the Dynastidæ, Melolontha, and the larva of Dytiscus,
there are fourteen; sixteen in the Copridæ; eighteen in Dytiscus, and
probably the majority of Coleoptera, both larva and imago, and
Lepidoptera; and a pair to each segment except the last, in the Myriapods.
ii. Respiratory plates (Respiratoria). The nearest approach to spiracles is
made by those remarkable plates that are found in such larvæ of Diptera, as
in that state inhabit substances that might impede or altogether stop the
entrance or exit of the air by the ordinary spiracles, such as dead or living
flesh, dung, or the like. The Creator therefore, as he has seen it good for
wise reasons[209] to commission certain insects to feed on unclean food, has
fitted them for the offices that devolve upon them, and has placed their
orifices for breathing in plates at each extremity of the body. There are
usually two of these plates at the head, and two at the tail. In the grub of the
common flesh-fly (Sarcophaga carnaria), at the junction of the first
segment of the body with the second, two of these plates are planted, which
are concave and circular, with a denticulated margin; in the cavity near the
lower side is a round spiracle. These plates the animal can withdraw within
the body, so as to prevent this spiracle from being stopped up by any greasy
substance[210]. The posterior extremity of this grub is truncated, and has a
large and deep cavity surrounded by several fleshy prominences: at the
bottom of this are two oval brown plates, in each of which are three oval
spiracles, placed obliquely: by the contraction of the fleshy prominences,
this cavity also can be closed at the will of the animal[211]. In some cases,
several stiff rays or spines replace the prominences[212]. In Echinomyia
grossa and others the anal plates appear not to be perforated, being
surmounted only by a central boss[213]; but this, most probably, as in the
case of Œstrus Ovis[214], is a valve that closes the respiratory orifices. In the
gad-fly of the ox (Œ. Bovis) there are no plates at the anterior extremity of
the body; but those planted in the other end are very remarkable, and
demand particular attention. Each is separated by a curved line into two
unequal portions; the smallest of which is contiguous to the convex belly,
and the largest to the concave back of the animal. This last is distinguished
by two hard, brown, kidney-shaped pieces, a little elevated with the
concave sides turned towards each other: in this sinus is a single, small,
white spot, which appears to be a spiracle: in the smallest portion are eight

minute circular orifices, arranged in a line[215]. As the only communication
which this grub has with the atmosphere is at its anal extremity, it has no
occasion for respiratory organs at the other. The gad-fly of the horse
(Gasterophilus Equi, &c.) which has no communication at all with the
external air, breathing that which is received into the stomach, has these
plates at both ends of the body.

iii. Respiratory Appendages[216]. These may be divided into two kinds;
those by which the animal has immediate communication with the
atmosphere, and those by which it extracts air from water.
1. To begin with the first. These are often found in insects which, during
their two first states, live in the water. No better example, nor one more
easy to be examined, of this structure, can be selected, than the gnat
(Culex). You must have occasionally observed in tubs of rain-water,
numerous little wriggling worm-like animals, which frequently ascend to
the surface; there remain a while, and then bending their head under the
body rapidly sink to the bottom again. These are the larvæ of some species
of the genus just named; and if you take one out of the water and examine
it, you will perceive that it is furnished near the end of its body with a
singular organ, which varies in length according to the species, and forms
an angle with the last segment but one[217]. The mouth of this organ is
tunnel-shaped, and terminates in five points like a star; and by this it is
usually suspended at the surface of the water, and preserves its
communication with the atmosphere: in its interior is a tube which is
connected with the tracheæ, and terminates in several openings, visible
under a microscope, at the mouth of the organ. The points or rays of the
mouth when the animal is disposed to sink in the water, are used to close it,
and cut off its communication with the atmosphere. When the animal is
immersed, a globule of air remains attached to the end of the tube, so that it
is in fact of less specific gravity than that element, and it is not without
some effort that it descends to the bottom; but when it wishes to rise again,
it has only to unclose the tube, and it rises without an effort to the surface,
and remains suspended for any length of time. Its anal extremity is clothed
with bunches of hairs, which are furnished with some repellent material
which prevents their becoming wet[218]: it is this repellent quality that

probably causes a dimple or depression of the surface, which if you look
narrowly you will discover round the mouth of the tube[219].
When the gnat undergoes its first change and assumes the pupa, instead of a
single respiratory appendage it is furnished with a pair, each in shape
resembling a cornucopia, and, what is remarkable, placed near the opposite
extremity of the body, for they proceed from the upper side of the trunk[220].
By these tubular horns, which Reaumur compares to asses' ears[221], they
respire, and are suspended at the surface.
Other respiratory tubes or horns are more complex. The rat-tailed grub of a
fly (Helophilus pendulus), like the gnat, breathes by a tube: but as if the
Creator willed to show those whose delight it is to investigate his works,
by how many varying processes he can accomplish the same end, this
respiratory organ is of a construction totally different from that we have
been considering. It is not fixed to the side of the tail, but is a continuation
of the tail itself, and is composed of two tubes, the inner one, like the tube
of a telescope, being retractile within the other[222]. The extremity, which is
very slender, and through which the air finds admission by a pair of
spiracles, terminates in five diverging hairs or rays, which probably
maintain it in equilibrio at its station at the surface[223]. As these larvæ seek
their food amongst the mud at the bottom of shallow pools, in which they
are constantly employed, they require an apparatus capable of being
lengthened or shortened, to suit the depth of the water, that they may
maintain their necessary communication with the atmosphere; and for this
purpose a single tube would not have been sufficient: therefore Providence
has furnished them with two, and both are extremely elastic, consisting of
annular fibres, so as to admit their being stretched to an extraordinary
length. Reaumur found that these animals could extend their tails to near
twelve times their own length. The mechanism by which the terminal piece
is pushed forth or retracted, is very curious, though extremely simple. Two
large parallel tracheæ, the direction of which is from the head[224] of the
grub to its tail, occupy a considerable portion of its interior: near the origin
of the tail, where they are very ample, they suddenly grow very small, so as
to form a pair of very slender tubes, but so long that, in order to find room
in a very contracted space, they form numerous zigzag folds attached to the
terminal tube; when this issues from the outer tube they consequently begin

to unfold, and when it is intirely disengaged, they are become quite straight
and parallel to each other. Reaumur has figured them as being united at the
base of the inner tube[225]; most probably, however, they do not here stop
short, but, as in other instances, proceed to the end, and terminate in the two
spiracles mentioned above: he conjectures that when the animal has
occasion to push forth its respiratory apparatus, it injects into these vessels
part of the air contained in the body of the tracheæ, which of course would
cause them to unfold and push forth the tube[226]. When this insect assumes
the pupa, instead of its anal respiratory organ it has four respiratory horns in
the trunk near the head[227].
The larva of the chamæleon-fly (Stratyomis Chamæleon) is furnished with a
respiratory organ of a still different and more elegant structure, exhibiting
some resemblance to the tentacula of what are called sea anemones. In this
larva the last joint of the body is extremely long, and terminates in an
orifice to receive the air, which is surrounded by a circle of about thirty
diverging rays, consisting of beautifully feathered hairs or plumes[228]. This
apparatus serves the same purpose with that above described of the larva of
the gnat. The feathery hairs are so prepared as to repel the water, and thus to
suspend the animal by its tail at the surface, and preserve a constant access
of air. When it has occasion to sink, it turns these hairs in and shuts the
orifice, carrying down with it an air-bubble that shines like quicksilver, and
which Swammerdam conjectures enables it again to become buoyant when
it wants to breathe[229].
In the red aquatic larva of a small gnat (Chironomus plumosus) there are
two anal respiratory subcylindrical horns, with the orifice fringed with
hairs[230]; and in another gnat Reaumur discovered four[231]. The larva of
Tanypus maculatus, whose remarkable legs I formerly noticed[232], exhibits
in the interior of its trunk two long, oval, opaque bodies, which De Geer
conjectures may be air-reservoirs; these, when the animal assumes the pupa,
according to every appearance become external, and are placed on the back,
precisely where the respiratory horns of aquatic pupæ are usually situated,
—they appear to terminate in a transparent point[233]. The pupa of a Tipula
observed by Reaumur, instead of two has only one of these respiratory
organs, in the form of a very fine hair proceeding from the anterior end of
the trunk, and considerably longer than the animal itself[234].

It is observable that aquatic insects that come to the surface of the water for
air, receive it at the anus, often carrying it down with them as a brilliant
bubble of quicksilver. This is generally done by means of spiracles in
perfect insects, but in the water-scorpion tribe in that state respiration is by
means of a long hollow tube, consisting of two concavo-convex pieces
which apply exactly to each other. This is found in both sexes, and therefore
cannot be an ovipositor, as some have thought[235].
These respiratory organs, however, are not invariably confined to aquatic
larvæ and pupæ, for those of some aphidivorous flies have anal ones, and
the pupa of Dolichopus nobilitatus, or a fly nearly related to it, which is
terrestrial, has likewise a pair of long sigmoidal ones on the back of the
trunk[236]. The pupa also of the rat-tailed larva just noticed as having four
horns, resides under the earth, the insect being only aquatic in its grub
state.
2. I am next to consider those respiratory appendages by which aquatic
insects, since they do not come to the surface for that purpose, appear to
extract air for respiration from the water; so that they may be looked upon
in some degree as analogous to the gills of fishes: there is, however, this
difference between them—in fishes, the blood is conveyed in minute
ramifications of the arteries to the surface of the branchial laminæ, through
the membranes of which they abstract the air combined with the water; but
as insects have no circulation, the process in them must be different, and
their branchiform appendages may be regarded as presenting some analogy
rather than any affinity to those of fishes. The first approach to this structure
is exhibited by the pupa of a gnat lately mentioned (Chironomus plumosus);
for on each side of the trunk this animal has a pencil consisting of five hairs
elegantly feathered, which, when they diverge, form a beautiful star; its
anus also is furnished with a fan-shaped pencil of diverging hairs[237].
On most of the abdominal segments of the larvæ and pupæ of the
Trichoptera are a number of white membranous floating threads, arranged
in bundles, four on each segment, two above and two below, and traversed
longitudinally by several air-vessels or bronchiæ, which run in a serpentine
direction, growing more slender as they approach the extremity, and in
some places sending forth very fine ramifications,—these are their
respiratory organs[238]. The caterpillar also of a little aquatic moth

(Hydrocampa stratiotata) at first sight appears to be covered on each side
with hairs, but which examined under a microscope are found to be
branching flattish filaments, each furnished with tubes from the tracheæ.
These caterpillars have also the semblance of spiracles, but apparently
found in the usual situation[239]. The larva of a little beetle often mentioned
in my letters (Gyrinus Natator), is furnished on each side of every
abdominal segment with a long, hairy, slender, acute, conical process, of the
substance of the segment, through each of which an air-tube meanders; the
last segment but one has four of these processes, longer than the rest[240].
Laminose or foliaceous respiratory appendages distinguish the sides of the
abdomen of the larvæ and pupæ of the Ephemeræ, whose history you found
so interesting[241]. In them these organs wear much the appearance of gills.
In the different species they vary both in their number and structure. With
regard to their number, some have only six pair of them, while others have
seven. In their structure the variations are more numerous, and sometimes
present to the admiring physiologist very beautiful forms[242]. They usually
consist of two branches, but occasionally are single, with one part folding
over the other, as in one figured by Reaumur, which precisely resembles the
leaf of some plant, the air-vessels or bronchiæ in connexion with the
tracheæ branching and traversing it in all directions, like the veins of
leaves[243]. The double ones differ in form. In the larva and pupa of
Ephemera vulgata there are six of these double false gills on each side of
the abdomen, the three last segments being without them; each branch
consists of a long fusiform piece, rather tumid and terminating in a point,
which is fringed on each side with a number of flattish filaments, blunt at
the end. An air-vessel from the trachea enters the gill at its base; is first
divided into two larger branches, each of which enters a branch of the false
gill. These branches send forth on each side numerous lesser ramifications,
one of which enters each of the filaments[244]. In another species (E.
vespertina) each false gill presents the appearance of a pair of ovate leaves
with a long acumen, and the air-vessels represent the midrib of the leaf,
with veins branching from it on each side[245]; and, to name no more, in E.
fusco-grisea, one branch represents the leaf of a Begonia, the sides not
being symmetrical, with its veins, while the other consists only of numerous

branching filaments[246]. In other aquatic larvæ, as in that of the common
May-fly (Sialis lutaria), these appendages consist of several joints[247].
By the above apparatus these aquatic animals are enabled to separate the air
from the water, as the fish by their gills; but how this separation is made has
not been precisely explained. The false gills in many species are kept in
continual and intense agitation. When they move briskly to one side,
Reaumur conjectures they may receive the air, and when they return back
they may emit it[248]. This brisk motion probably disengages it from the
water. In many species, when in repose, they are laid upon the back of the
animal[249], but in others they are not[250].
The larvæ of the Agrionidæ appear to respire like those of the Ephemeræ,
&c. by means of long foliaceous laminæ or false gills filled with air-vessels;
but instead of being ventral, they proceed from the anus. They are three in
number, one dorsal and two lateral, perpendicular to the horizon, of a
lanceolate shape, beautifully veined, with a longitudinal middle nervure,
from which others diverge towards the margin, which are probably
bronchiæ. They are used by the animal, which swims like a fish, as fins, but
it does not appear to imbibe the water like the other Libellulinæ, nor to
propel itself by ejecting it,—a circumstance which furnishes an additional
argument for the more received opinion, that this action in them is for the
purpose of respiration as much as for motion[251].
The larvæ and pupæ of the Libellulinæ, receive the water and air that they
respire by a large anal aperture, which is closed at the will of the animal by
five hard, moveable, triangular, concavo-convex pieces, all very acute and
fringed with hairs. These pieces are placed so that there is one above, which
is the largest of all; one on each side, which are the smallest, and two
below; when these are closed they form together a conical point[252].
Sometimes only three of these pieces are conspicuous[253]: three other
cartilaginous pieces, resembling the valves of a bivalve shell, close the
passage within the pointed pieces[254]. At this orifice the water is received;
and when, by an internal process to be described afterwards, it has parted
with its oxygen, is again expelled.
Under this head I shall mention a fact which may be connected with
respiration of the insects concerned. In dissecting a moth related to

Catocala Pronuba, but I do not recollect the particular species,—at the base
of the abdomen of the male I discovered two bunches of long fawn-
coloured parallel hairs, planted each in an oval plate, plane above, but
below convex and fleshy; while the plates remained attached to the insect,
they appeared to have a distinct pulsation. The hairs, which are about half
an inch long, diverge a little, and form a tuft not very unlike a shaving-
brush[255]. I have not since met with this species, but I have preserved the
brush and scale. Somewhere in Bonnet's works, but I do not recollect
where, I have since found mention of a similar fact in another moth.
II. Having considered the external respiratory organs of insects, by which
the air is received, we are next to consider the internal ones, by which it is
distributed. These are gills; tracheæ and bronchiæ; and sacs or pouches[256].
i. Gills (Branchiæ[257]). Having lately described what may be denominated
false gills, or branchiform appendages, I shall now call your attention to
what may be denominated true ones, which are peculiar to the Arachnida
Class: but what is remarkable, the animals that breathe by them are very
rarely inhabitants of the water, so that their functions cannot be perfectly
analogous to those of fishes.
In the Scorpion, on each side of the four first ventral segments a spiracle
may be discovered, which has no lip as in other insects, but is merely a
circular orifice. These orifices do not lead to tracheæ or vesicles, but to true
gills, which are situated below a muscular web which clothes the internal
surface of the crust. Each gill consists of many semicircular very thin
plates, of a dead milky white, which are connected together at the dorsal
end like the leaves of a book. There appear to be more than twenty of these
leaves, which when strongly magnified look transparent and destitute of any
vessels. Each gill is fastened at the back to the spiracle[258]. In the spiders
also, gills are discoverable, but differently circumstanced. On the under side
of the abdomen, near the base, is a transverse depression, on each side of
which is a longitudinal opening leading to a cavity, which is covered from
above by a cartilaginous plate. In this cavity is situated a true gill, which is
white, triangular, and covered with a fine skin; the leaves of this gill are far
more numerous and much finer and softer than those of the gills of the
scorpion. On account of their softness they have often the appearance of a

slimy skin; but their laminated structure shows itself very clearly in old
specimens, and in such as have been immersed in boiling water[259].

ii. Tracheæ and Bronchiæ[260]. Parallel with each side of the body of most
insects and extending its whole length, run two cylindrical tubes[261], which
communicate with the spiracles[262], and from which issue, at points
opposite to those organs, other tubes which ramify ad infinitum, and are
distributed to every part of the body[263]. The first of these tubes are called
the tracheæ and the latter the bronchiæ. This structure appears, however,
not to be universal: it is to be found in caterpillars and many Dipterous
larvæ; but in that of the rhinoceros-beetle and other Lamellicorns, the
bronchiæ branch directly from the spiracle, the bottom or interior mouth of
which is lined by a membrane from which they proceed[263]: something
similar has been observed to take place in many insects in other states, as
the common cockchafer[264]; in the pupa of Smerinthus Populi[265]; in the
Cicadæ[266]; in the Locust tribe[267]; and many others. In the Cossus, or
larva of the great goat-moth, the trachea commences with the first spiracle,
and finishes a little beyond the last, after which it diminishes considerably
in diameter, and terminates in several branches or bronchiæ, which proceed
to the anal extremity of the body[268]. The bronchiæ which originate from
the tracheæ in the vicinity of each spiracle, may be considered as consisting
in general of three packets;—dorsal ones, which are distributed to the back
and sides of the animal; visceral ones, which enter the cavity of the body,
and are lost amongst the viscera and the caul; and ventral ones, which
dipping from the tracheæ overrun the lower part of the sides and belly[269].

The tracheæ and bronchiæ consist of three tunics[270]: the first or external
one is a thickish membrane, strengthened by a vast number of fibres or
vessels, which form round it a number of irregular circles; the second is a
membrane more thin and transparent, without a vascular covering[271]; the
third is formed of a cartilaginous thread running in a spiral direction, which
may be easily unwound[272]. This structure gives a great elasticity to these
organs, so that they are capable of considerable tension, after which they
return to their usual length[273]. The Bronchiæ are cylindrical or slightly
conical, insensibly diminishing in size as they leave the trunk, in which they
originate. In larvæ, after losing their spiral fibre, they appear to terminate in

membrane, but in perfect insects they pass into vesicles[274]. In the Cossus
the trachea is flattened, and in every segment, except the first and two last,
is bound by a fleshy cord four or five times as thick as its threads. Where
this occurs, there is a slight constriction,—probably here is a sphincter, by
the contraction of which Lyonet supposes the trachea may be shut when it
is necessary to stop the passage of the air, and direct it to any particular
point[275]. The structure here described is admirably adapted for the purpose
it is intended to serve; for had these vessels been composed of membrane,
they could not possibly have been prevented from collapsing; but by the
intervention of a spiral cartilaginous thread this accident is effectually
guarded against, and the necessary tension of the tubes provided for.
However violent the contortions of the insect, however small the diameter
of these vessels, they are sure to remain constantly open, and pervious to
the air. And by this circumstance they may be always distinguished from the
other organs of the animal, and likewise by their pearly or silvery hue, for
from being constantly filled with air, these tubes, when viewed under a
powerful microscope in a recently dissected insect, present a most beautiful
and brilliant appearance, resembling a branching tree of highly polished
silver or pearl:—though sometimes they are blue, or of a lead colour, and
sometimes assume a tint of gold. In the dead insect the larger tubes soon
turn brown, but the finer ones preserve their lustre several weeks[276]. The
ramifications of the tracheal tree may be seen without dissection through
the transparent skin of the common louse[277] and most of the thin skinned
larvæ.
You will not expect to view in this way the minuter ramifications of the
bronchiæ, when I have mentioned their number and incredible smallness.
Nothing but the scalpel of a Lyonet and the most powerful lenses are
adequate to trace the extremities of these vessels; and even with every help,
they at last become so inconceivably slender as to elude the most piercing
sight. That illustrious anatomist found that the two tracheæ of the larva of
the Cossus gave birth to 236 bronchial tubes, and that these ramify into no
less than 1336 smaller tubes, to which, if 232, the number of the detached
bronchiæ, be added, the whole will amount to 1804 branches[278].
Surprising as this number may appear, it is not greater than we may readily
conceive to be necessary for communicating with so many different parts.
For, like the arterial and venous trees, which convey and return the blood to

and from every part of the body in vertebrate animals, the bronchiæ are not
only carried along the intestines and spinal marrow, each ganglion of which
they penetrate and fill, but they are distributed also to the skin and every
organ of the body, entering and traversing the legs and wings, the eyes,
antennæ, and palpi, and accompanying the most minute nerves through
their whole course[279]. How essential to the existence of the animal must
the element be that is thus anxiously conveyed by a thousand channels, so
exquisitely formed, to every minute part and portion of it! Upon
considering this wonderful apparatus we may well exclaim, This hath God
wrought, and this is the work of his hands.
Though in general there is only a pair of tracheæ, yet in some larvæ a larger
number have been discovered. In those of the Libellulinæ there are six.
According to M. Cuvier, Reaumur, who mentions only four, overlooked the
two lateral ones that are connected with the spiracles[280]. The reason of this
and other parts of their internal structure I shall explain under the next head.
In the grub of the gad-flies of the horse (Gasterophili,) Mr. B. Clark
discovered eight longitudinal tracheæ,—six arranged in a circle and two
minute ones, which appeared to him to terminate in a pair of external
nipples (spiracles) in the neck of the animal[281]. This is a singular anomaly,
as the other Œstridæ have only a pair of tracheæ[282].
iii. Respiratory Sacs or Pouches. Besides their tracheæ and bronchiæ, many
insects are furnished with reservoirs for the air, under the form of sacs,
pouches, or vesicles. These are commonly formed by the bronchial tubes
being dilated at intervals, especially in the abdomen, into oblong inflated
vesicles; from which other bronchial tubes diverge, and again at intervals
expand into smaller vesicles, so as to exhibit no unapt resemblance—as
Swammerdam has observed with respect to those of the rhinoceros-beetle—
to a specimen of Fucus vesiculosus. Cuvier compares them in the
Lamellicorn beetles in general to a tree very thickly laden with leaves[283];
and Chabrier observes that they particularly occur in the intestinal
canal[284]. This structure of the pulmonary organs may be seen also in the
common hive-bee, and other Hymenoptera; but the vesicles are less
numerous, and those at the base of the abdomen much larger than the
rest[285]. These vesicles, by a very rough dissection, may be distinctly seen
in the abdomen of the cockchafer, which appears to be almost filled with

them. Not being composed of cartilaginous rings like the air-tubes, but of
mere membrane, if a pin pierces one, the air that inflates it escapes, and it
collapses. In the larva of a little gnat (Corethra culiciformis) the tracheæ
appear to proceed from a pair of oblong vesicles of considerable size[286] in
the trunk, and towards the anus they form two other smaller ones[287],—
upon piercing the former, De Geer observed a considerable quantity of air
to make its escape[288]. Another species, probably of the same genus,
described by Reaumur, exhibits something similar[289].
But one of the most remarkable structures, in this respect, is to be seen in
the larva and pupa of the dragon-flies (Libellulina). I have before noticed
the number of their tracheæ, but I shall here describe their whole internal
respiratory apparatus. I must observe that Reaumur, Cuvier, and most
modern writers on the physiological department of Entomology, have
affirmed that they respire the water, and that they receive it for that purpose
at their anal extremity: but M. Sprengel, from having observed in the larvæ
abdominal spiracles, is unwilling to admit this as a fact[290]; and De Geer
also seems to hesitate upon it, especially as he discovered that the animal
seemed to absorb the water to aid it in its motions[291]. But when we
consider that it is by the action of a pneumatic apparatus that the absorption
and expulsion of the water takes place, and that the animal when it has been
taken out of that element, upon being restored to it, immediately has eager
recourse to this action[292], we shall feel inclined rather to adopt the opinion
of those great physiologists Reaumur, Lyonet, and Cuvier, and admit that it
absorbs water for the purpose of respiration. I shall now explain how this
takes place. The pieces both internal and external that close the anal orifice
have been before described; the others employed in the admission and
expulsion of the water are evidently respiratory organs. When this orifice is
opened, the parts that are above it are drawn back in an opposite direction,
so that the five last segments of the abdomen become entirely empty, and
form a chamber to receive the water that enters by it. When the water is to
be expelled, the whole mass of air-vessels which had receded towards the
trunk, is pushed forwards, and forms a piston that again expels the water in
a jet. It consists of an infinite number of bronchiæ, entangled with each
other, which proceed from the middle and posterior end of the tracheæ. M.
Cuvier in the interior of the rectum of the larva discovered twelve
longitudinal rows of little black spots, in pairs, which exhibited the

resemblance of six pinnated leaves. These are minute conical tubes, of the
spiral structure of tracheæ, which decompose the water, and absorb the air
contained in it. He also discovered that each of these tubes gave birth to
another outside the rectum, which connected itself with one of the six great
longitudinal tracheæ; two of which are of enormous size, and appear to
serve as reservoirs, since they furnish air by transverse branches to two
other tubes; they have each a recurrent branch, which follows the course of
the intestinal canal, and furnishes it with an infinity of bronchiæ[293]. These
tracheæ are found in the perfect insect. The principal ones in some send
forth many branches, terminating in vesicles, which in shape resemble the
seed-vessels of some species of Thlaspi, while others appear to form a file
of oblong ones[294]. Near each of their spiracles also is a vesicle which
appears to be a reservoir[295].
But this kind of structure is not confined to insects strictly aquatic. Even
such species of terrestrial ones as live upon aquatic plants, and are,
consequently, necessarily or accidentally often a considerable time under
water, are furnished with some apparatus by means of which they can exist
in this element for a considerable period. For example, most of the Weevils
(Rhyncophora) die in a short time if immersed in water; yet the species of
the genera Tanysphyrus, Bagous, and Ceutorhynchus which feed on aquatic
plants, can exist for days under water, as I have ascertained by experiment.
C. leucogaster and another of the same tribe, swims like a Hydrophilus, and
will live a long time in a bottle filled with water and corked tight. Other
insects also, that are not at all aquatic, have pneumatic pouches. A striated
or channeled vesicle I have found under the lateral angles of the collar in
the humble-bee, where Chabrier supposes the vocal spiracles are situate;
and also at the mouth of the spiracles of the metathorax in Vespa, &c.[296] In
Sphinx Ligustri the bronchiæ terminate in oblong vesiculoso-cellular
bodies, almost like lungs[297]; in Smerinthus Tiliæ these are preceded by a
simple vesicle bound with spiral fibres[298]. M. Chabrier thinks that these
air-bladders of insects, amongst other functions, give more fixity and force
to the muscles for flight[299].
Many physiologists have seen an analogy between the spiral vessels of
plants and the tracheæ of insects; and some of great name, as Comparetti,
Decandolle, and Kieser, have thought that in some instances they

terminated in the oscula or cortical pores: but Sprengel contends that they
are not accurate in this opinion[300]. In fact, the principal analogy seems to
be in the spiral structure of both these vessels.

Having considered the different organs of respiration both external and
internal, I shall make a few further observations upon this function. We
know little more respecting the mode in which insects respire, except that
they breathe out the air by the same kind of organs by which they receive it,
—namely, the spiracles, or their representatives. This has been satisfactorily
proved by Bonnet, who showed that the experiments by which Reaumur
thought it established that insects inspire by their spiracles, but expire
through the mouth, anus, or pores of the skin, are founded on an erroneous
assumption. This physiologist, having observed on the surface of
submerged insects numerous bubbles of air, concluded that they had passed
through the above orifices[301]: but Bonnet found by various experiments
carefully conducted, that this appearance was caused by air which adhered
to the skin and its hairs, and that when the access of this was precluded by
carefully moistening the skin with water previously to immersion, this
accumulation of air-bubbles on its surface did not take place[302]. And in a
variety of instances he observed large ones issue from all the spiracles,
especially the anterior ones. These bubbles sometimes were alternately
emitted and absorbed without quitting the spiracle[303], and at others were
darted with force to the surface of the water, where they appeared to burst
with noise[304]. This author is of opinion that the first and last pair of these
organs are of most importance to respiration[305]. Reaumur subsequently
owned that Bonnet's arguments had shaken his opinion[306]; and some
observations of his own, with respect to the respiration of the bot of the ox,
go to prove that expiration and inspiration are not by the same spiracles; for
he found that the air in this animal was expired by the eight little lower
orifices before mentioned[307], from which he clearly saw the air-bubbles
issue—the upper one he conjectures receives the air[308]. As the only
communication that this grub has with the atmosphere is by its posterior

extremity, it follows, reasoning from analogy, that the anterior respiratory
plates of Dipterous larvæ, which may be regarded as representing the
spiracles of the trunk in insects in general, are destined for the escape of the
air, after it has parted with its oxygen, received by the anal ones[309]. So that
there seems very good ground for M. Chabrier's opinion that inspiration is
ordinarily by the abdominal spiracles, and expiration by those of the trunk
of insects[310]. He seems to have been led to the adoption of this opinion,
not so much by experiments similar to that of Reaumur just stated, but by
observing that in many instances these two sets of spiracles differ from each
other, the latter having a convex and the former a concave mouth or bed[311].
In some cases, however,—for instance during flight,—he supposes the
spiracles of the trunk may receive as well as emit the air[312]: he likewise is
of opinion, and it seems not improbable, that by means of these openings in
the trunk, from the rush of the superfluous air through them, insects
produce those sounds for which they are remarkable,—as the humming of
bees and flies. In the former he thinks the sound is produced by the
pneumatic apparatus covered by the ends of the collar; while in the latter he
attributes it to the spiracles in the metathorax behind the wings attended by
a poiser[313]. I incline, however, to M. Dufour's opinion[314],—that the vocal
spiracles in the Hymenoptera, as well as in the Diptera, are those behind the
wings. Perhaps both theories may be right; for if you take any common
humble-bee, you will find that, in the hand, it produces one kind of sound
when its wings are motionless, and another more complex and intense when
they vibrate. In numerous instances, however, there is no very striking
external difference between the spiracles of the trunk and those of the
abdomen: this observation applies more particularly to the caterpillars of
Lepidoptera; but whether these receive the air by those of the abdomen, and
return it by those of the trunk, has not yet been ascertained; and indeed, too
little is at present known upon the subject, and too few facts have been
collected, to admit of dogmatizing.
The external signs of respiration in insects are not universally to be
discovered. The alternate contraction and expansion of the abdomen is,
however, very visible in some beetles, bees, the larger dragon-flies, and
grasshoppers. In one of the latter, Acrida viridissima, Vauquelin observed
that the inspirations were from fifty to fifty-five times in a minute in
atmospheric air, and from sixty to sixty-five when in oxygen gas[315]. But

M. Chabrier has given the most satisfactory account of these signs: The
abdomen, says he, is the principal organ of inspiration; it can dilate and
contract, lengthen and shorten, elevate and depress itself. In flight, in
elevating its extremity at the same time with the wings, it contracts itself,
pushes the air into the trunk, and diminishes the weight of the body by the
centrifugal ascending force[316]. In the majority of insects perhaps the
dilatation of the abdomen takes place by the recession of the segments from
each other by means of the elastic ligaments that connect them; in others, as
the Dynastidæ, Galeodes, &c. by the longitudinal folded membrane that
unites the dorsal and ventral segments—in the Libellulina by similar ventral
folds; and in Cimbex by membranous pieces in the first dorsal segment,
which De Geer observed was elevated and depressed at the will of the
animal[317].
Air is as essential to insects in their pupa as in their larva or perfect states.
Lyonet, however, Musschenbroek, Martinet, and some other physiologists,
have doubted whether quiescent pupæ breathed[318]; but Reaumur and De
Geer seem to have proved that they do[319]: and if thrown into water, the
same proof of respiration, by the emission and retraction of a bubble of air
takes place, as in the larvæ; and De Geer found that if one be transferred
under water from one spiracle to another, it will be absorbed by it[320].
Indeed, unless these pupæ had breathed, where would have been the
necessity for the spiracles with which all are furnished? It is remarkable,
however, that all these spiracles do not seem of equal importance in this
respect. Reaumur found that if the posterior spiracles only were closed with
oil, the insect suffered no injury; but that if the anterior ones were similarly
treated, it infallibly died[321]. The respiration however of pupæ seems more
perfect in those that have recently assumed that state, than in those that are
more advanced towards the imago; in which at first, from Reaumur's
experiments[322], it appears that the posterior spiracles were stopped; and in
others still older, from Musschenbroek's[323], even the anterior ones. Those
quiescent pupæ that during that state remain submerged, respire air. De
Geer has given an interesting record of this, in the case of Hydrocampa
stratiotata. This insect spins a double cocoon, the outer one thin, and the
inner one of a close texture. In the pupa there are three pair of conspicuous
spiracles on the second, third, and fourth segments of the abdomen, which

are placed on cylindrical tubes, and they appear to have no other air-vessels.
The respiratory gills of the larva having vanished, like some others of the
same genus, they know how to surround themselves with an atmosphere of
air in the midst of the water, so that the interior of their inner cocoon is
impervious to the latter element—how they renew the air has not been
ascertained. Though they respire air, water is equally necessary, for the
animal died when kept out of water[324].
The great majority of insects respire in much the same manner in all their
states, particularly as to their external organs; for when the larva breathes
by the lateral spiracles, the pupa and imago usually do the same. The
converse of this, however, by no means holds; for it not unfrequently
happens that the two latter breathe by means of lateral spiracles, though
they received the air in their larva state by an apparatus altogether different.
Thus the larvæ of many Diptera breathe by an anal tube, while the pupa and
imago follow the general system. Sometimes a tribe of insects breathe by an
apparatus quite different in all their states, as we have seen to be the case
with the common gnat[325], which has an anal respiratory tube in its first
state, thoracic respiratory horns in its second, and the ordinary lateral
spiracles in its third.
Changes also take place in their internal organs. In the larvæ the respiratory
apparatus, especially the tracheal tubes, is often much larger and more
ramified than in the imago; and as the former is the principal feeding state,
there seems good ground for Mr. B. Clark's opinion—that the respiration is
intimately connected with the conversion of the food[326]. In the imago,
there appears to be more provision for storing up the air in vesicular
reservoirs, than in the larva. Wonderful is the mode in which some of the
changes in the internal structure, which these variations indicate, must
necessarily take place. They are, however, probably not more singular than
those which less obviously occur in the air-vessels of all insects in their
great change out of the larva into the pupa state. But having before enlarged
on this subject, I need not repeat my observations[327].

The access of air is as necessary to insects even in their egg state[328], and in
many cases its presence seems provided for with equal care, by means as
beautiful as those Sir H. Davy and Sir E. Home have shown to occur in the

oxygenation of the eggs and fœtuses of vertebrate animals[329]. It is only
necessary to view the admirable net-work of air-vessels which
Swammerdam discovered spread over the surface of the eggs of the hive-
bee while in the ovaries[330],—a provision which, from analogy, we may
conclude obtains generally; from the importance which nature has attached
to the oxygenation of the germ while in the matrix. And judging from
analogy, we may infer that the access of this element is as carefully secured
after the egg is laid, as before. The eggs of most insects being of a porous
texture, often attached to the leaves of plants, and some of them embedded
in the very substance of a leaf or twig[331], are in a situation for the
abundant absorption of oxygen: and the pouch of silk in which the eggs of
spiders and Hydrophili are deposited, may probably, from Count Rumford's
experiments, be of utility in the same point of view. In the case of the
Trichoptera and other insects[332] whose eggs are dropped into the water
enveloped in a mass of jelly, this substance perhaps serves for aërating the
included embryo, in the same way with the jelly surrounding the eggs of the
frog, dog-fish, &c. It would be desirable to ascertain whether the former
jelly be of the same nature as the experiments of Mr. Brande have shown
the latter to be[333]. It is not improbable that the singular rays that terminate
the eggs of Nepa[334] may in some way be connected with the aëration of
the egg.

To what I have before remarked with regard to the vital heat of insects[335],
I may under this head very properly add a few further observations. I there
stated, that the temperature of these animals is usually that of the medium
they inhabit, but that bees, and perhaps other gregarious ones, furnish an
exception to this rule[336]. A confirmation of this remark is afforded by Inch,
a German writer, who, upon putting a thermometer into a bee-hive in
winter, found it stand 27° higher than in the open air; in an anthill, he found
it 6° or 7° higher; in a vessel containing many blister-beetles (Cantharis
vesicatoria,) 4° or 5° higher. A thermometer, standing in the air at 14° R.,
put into a glass vessel with Acrida viridissima, in nine minutes rose to 17°,
and a similar result was observed with respect to other insects[337]. Dr.
Martine says that caterpillars have but two degrees of heat above that of the
air they live in[338]. Coleopterous insects are said to move slowly and with
difficulty when the thermometer sinks to 36°, to become torpid at 34°, and

to lose muscular irritability at a lower degree[339]. I have before observed
that some insects will bear to be frozen into an icicle, and yet survive[340]:
they share this power with reptiles, fishes, and amphibia. But, however
small the excess of it in some insects above that of the medium they inhabit,
it proves that they possess the power of generating heat. Whether, like the
warm-blooded animals, they generally possess that of resisting heat by
perspiration, &c. is not so clear. Yet the heat to which some can bear to be
exposed, basking at noon, as Dr. Clarke informs us[341], on rocky and sandy
places, exposed to the full action of the sun, appears sufficient, if not
resisted by some principle of counteraction, to roast them to a cinder. That
bees perspire is well known, but probably not singly.
When the respiration of insects is suspended by immersion in any fluid, it is
often resumed, even when it has been long and they are apparently dead, if
they be brought into contact with the atmosphere. Reaumur found this to be
the case with bees[342]; and Swammerdam tells us that the maggot of the
cheese-fly (Tyrophaga Casei) lived six or seven days in rain-water[343]: he
found it so difficult to kill the larva of Stratyomis Chamæleon, which he
first immersed twenty-four hours in spirits of wine, and then put them
several days in water, without killing them,—that he lost his patience, and
dissected them alive. He tried to drown them also in vinegar, in which they
held out more than two days[344].
That the suspended animation and subsequent death of most terrestrial
insects when thrown into water is caused by the want of air, is evident from
this,—that the same effect ensues if the spiracles be covered with any oily
or fatty matter. In this case too, their vital powers soon become suspended:
they revive, if the suffocating matter be soon removed; and if this be not
done, infallibly perish. This fact was known to the ancients, for Pliny
observes that bees die if dipped in oil or honey[345]. One exception to this
law has been before mentioned[346]: a similar contrivance secures the
cheese-maggot from having its respiration interrupted by its moist and
greasy food; the grub also of Sarcophaga carnaria, and of other Muscidæ
probably, has its posterior spiracles placed in a plate at the bottom of a kind
of fleshy pouch, which has the shape of a hollow, truncated, and reversed
cone. This pouch the grub can close whenever it pleases, so as to cover its
spiracles[347]. And numerous other larvæ, both of Diptera and Coleoptera

that devour unclean and oily food, have doubtless some protection of this
kind for their spiracles and respiratory plates.
I am, &c.

LETTER XXXIX.
INTERNAL ANATOMY AND PHYSIOLOGY OF INSECTS,
CONTINUED.
CIRCULATION.

We learn from the highest authority, that the blood is the life of the
animal[348]: every object of creation, therefore, that is gifted with animal
life, we may conclude, in some sense, has blood, which in this large sense
may be defined—The fluid that visits and nourishes every part of a living
body[349]. But the Great Author of nature has varied the machinery by
which this nutritive fluid is formed and distributed, gradually proceeding
from the most simple to the most complex structure; in which he seems to
have seen it fit to invert the process observable in the systems of sensation
and respiration, where the ascent is from the most complex, to the most
simple structure. In the lowest members of the animal creation, the blood
seems the portion they imbibe of the fluid medium in which they reside,
which when chylified, distributes new molecules to all parts of their
frame[350]. In others, as in insects, it is formed by the chyle that transpires
through the intestinal canal into the general cavity of the body, where it
receives oxygen from the air-vessels, and is fitted for nutrition[351]. In these
animals it is accompanied by a long dorsal vessel, the first step towards a
heart, which alternately contracts and dilates with an irregular systole and
diastole, but appears to have no vascular system connected with it, though
in their preparatory states it has an extra-vascular circulation which ceases
in the perfect insect. Again: in others, as the Tubicoles, Annelida, &c., a real
circulation has been discovered; that is to say, a system of veins and
arteries, but unaccompanied by a muscular heart[352]. In the Arachnida and
Branchiopod Crustacea the long dorsal vessel is also found; but in these it
is connected with an arterial and venous system, which receives, distributes,
and returns the blood[353]. It has therefore now become a true heart, and
there is a regular circulation; and in the Decapod Crustacea the dorsal

vessel is contracted into an oval form, and placed nearly in the centre of the
trunk[354]. In the great majority of invertebrate animals the blood is white,
but in the Annelida, to which Class the common dew-worm belongs, a
curious anomaly takes place—for it is red[355]. Thus a gradual ascent is
made to the circulating system of the vertebrate and red-blooded animals. In
all, however, the blood is the principal instrument of nutrition and
accretion; and is on that account properly so denominated, though not
connected with a circulating system.
Having given you this general outline of the means by which the blood is
distributed in the different Classes of animals, I shall now confine myself to
the case of insects and Arachnida, beginning with the former.
I. If you examine attentively the back of any smooth caterpillar with a
transparent skin, you will perceive in that part an evident pulsation, as
though a fluid were pushed at regular intervals towards the head, along a
narrow tube which seems to run the whole length of the body. Accurate
dissections have proved that this appearance is real, that there is actually
present in the back of most insects, placed immediately under the skin and
furnished with numerous air-vessels, a longitudinal vessel[356] originating in
the head near the mouth[357], running parallel with the alimentary canal
nearly to the anus, containing a fluid which is propelled in regular
pulsations of from 20 to 100 per minute, more or less as the weather is
colder or warmer[358], causing a sensible alternate systole and diastole from
the anal extremity towards the head. In the Cossus these pulses were
observed by Lyonet to begin in the eleventh segment, from which they
passed from segment to segment, till they arrived at the fourth, where they
terminated[359]. This vessel is what Malpighi, who first discovered it,
termed a heart, or rather series of hearts[360]; but which Reaumur, who
injected it, regarded as a simple artery without striking contractions[361]:
but to steer clear of any hypothesis, I shall merely call it the dorsal vessel
(Pseudo-cardia). When carefully taken out of the body it is found to be a
membranous tube, appearing to be closed at each end[362], in many larvæ of
equal diameter every where, but in perfect insects usually widest at the anal
extremity[363], and attenuated into a very slender filament towards the head.
In some insects, however, as in the larva of the chamæleon-fly (Stratyomis
Chamæleon), it is attenuated at both ends, and in the Ephemera is

alternately constricted and dilated as Malpighi describes that of the
silkworm[364], a dilated portion belonging to each segment[365]. In the
Cossus, and probably others, after the third segment, it is furnished with
nine pair, the three posterior pair being the largest, of triangular transverse
bundles of muscular fibres, which Lyonet denominates its wings[366], the
action of which produces its systole and diastole, and their propagation
from the tail towards the head[367]. Under the last pair of these wings it is
strengthened by a large number of circular muscular fibres[368]. I have
stated it as appearing to be closed at each extremity, because Cuvier and
most writers have so regarded it, and probably it is so closed in the perfect
insect; but from Lyonet's words it should seem that, in the larva of the
Cossus, he considered it as open and expanded at its anterior end[369]. He
seems also to suspect, that, by means of what he calls the frontal ganglions,
a fluid is derived from the dorsal vessel to the spinal marrow. He likewise
describes a large nerve as passing through it and becoming recurrent[370].
Carus, as we shall soon see, has also proved that this tube is not closed in
larvæ.
The fluid which this vessel contains is very abundant; in the animal it
appears colourless and transparent like water, but when collected in drops it
becomes more or less yellow, and even orange[371]. Examined under the
microscope it appears filled with a prodigious number of transparent
globules, of incredible minuteness[372]. When mixed with water, which it
does readily, its globules lose all their transparency, and coagulate into
small clammy masses. After evaporation it becomes hard, and cracks like
gum, as blood does also. This gummy substance is so abundant, that the
fluid contained in the dorsal vessel of the caterpillar of the Cossus yields a
mass of it of the size of a grey pea[373].
From the situation of this dorsal vessel, which is precisely the same with
that of the heart in Arachnida and the Branchiopod Crustacea, and from the
systole and diastole which keep its fluid contents in constant motion, who
can wonder that the physiologists who first discovered it, reasoning
analogically, maintained that it was a true heart? But modern comparative
anatomists, and those of the highest name, from the absence of a vascular
system for a circulation, have contended that it is not a true heart, but an
organ appropriated to other purposes: a third hypothesis, and intermediate

between these two, has very recently been promulgated, that the organ in
question, namely, is a real heart, and in the preparatory states of insects, the
centre of a real circulation, which, in the imago state, ceases with the full
development of the wings; but that this circulation is extravascular, or
without peculiar vessels analogous to veins and arteries.
I shall now enlarge a little upon each of these hypotheses, beginning with
the first or original one.
No one will deny that the argument from analogy is strongly in favour of
this: I need not therefore dwell upon it, but proceed to others.
Swammerdam, to whose exactness in observing, and scrupulous accuracy,
every reader of his immortal work will bear testimony, expressly asserts
that he has seen vessels issuing from the dorsal vessel in the silkworm, and
even succeeded in injecting them with a coloured fluid[374]. Now it seems
extremely improbable that so practised and expert an anatomist should have
been deceived, especially upon a point which would naturally excite his
most earnest and undivided attention. Without this recorded experiment,
perhaps, it might be thought, though this was very unlikely, that he had
mistaken bronchiæ for veins and arteries: but how could they have been
injected from the supposed heart? Another great physiologist, Reaumur, in
the caterpillar of the saw-fly of the rose (Hylotoma Rosæ) observed, besides
the dorsal vessel, a ventral one of similar form, in which also was a
pulsation, but slower than that of the other. This he supposes may be the
principal trunk of the veins[375]. Bonnet thought he discovered a similar
vessel in a large caterpillar, but with all his attention could perceive no
motion in it[376]. Reaumur also fancied he perceived in the grub of Musca
vomitoria, in which he in vain looked for the dorsal vessel, a fleshy part
which exhibited alternate pulsations; and when with a pair of scissors he
made a lateral incision in the insect, amongst other parts that came out,
there was one that had movements of contraction and dilatation for several
minutes,—this experiment was repeated with the same result upon several
grubs[377]. De Geer, whose love of truth and accuracy no one will call in
question, saw the appearance of blood-vessels in the leg of the larva of a
Phryganea L. (as Lyonet did in those of a flea[378]); and in the transparent
thigh of Ornithomia avicularia he discovered a pulse like that of an
artery[379]. Baker, whose only object was to record what he saw, speaks of

the current of the blood being remarkably visible in the legs of some small
bugs[380]: what he meant by that term is uncertain, but they could not be
spiders, which he had just distinguished. This author has likewise seen a
green fluid passing through the vessels of the wings of grasshoppers[381];
and M. Chabrier is of opinion that insects possess the power of propelling a
fluid into the nervures of their wings and withdrawing it at pleasure, as they
are elevated or depressed[382]; but this last fact may be independent of a
circulation.
But though these arguments, which I have stated in their full force, appear
strong, and at first sight conclusive, those which may be urged for the more
modern opinion—that no circulation exists in insects, properly so called,—
appear to have still greater weight. Lyonet, whose piercing eye and skilful
hand traced the course of so many hundred nerves and bronchiæ long after
they became invisible to the unassisted eye, and which were a thousand
times smaller than the principal blood-vessels, opening into so large an
organ as the supposed heart of insects, might be expected to be, could never
discover any thing like them. His most painful researches, and repeated
attempts to inject them with coloured liquors, were unable to detect the
most minute opening in the dorsal vessel, or the slightest trace of any artery
or vein proceeding from or communicating with it[383]. And Cuvier, whose
unrivalled skill in Comparative Anatomy peculiarly qualified him for the
investigation, repeated these inquiries, and tried all the known modes of
injection, with equal want of success; and is thus led to the conclusion, that
insects have no circulation, that their dorsal vessel is no heart, and therefore
ought not to be called by that name: that it is rather a secretory vessel, like
many others of that kind in those animals. As to the nature of the fluid that
it secretes, and its use, he thinks it impossible, from our present information
on the subject, to form any satisfactory conclusion[384]. Marcel de Serres
informs us—which further seems to prove that it can be no real heart—that
this vessel may be totally removed without causing the immediate death of
the insect[385]. This opinion receives additional confirmation from the mode
in which respiration is performed in insects. In those animals that have a
circulation, this takes place by means of lungs or gills;—thus we find, even
in the Crustacea and Arachnida so nearly related to insects, that the organs
of this function are true gills; whereas in insects, though in some of their
states their respiratory tubes are branchiform, yet they are not gills, and the

respiration is by tubes and spiracles. And these tubes, as you have seen, are
so numerous and so infinitely ramified and dispersed, as to occupy the place
of arteries and veins, and to imitate their distribution,—and thus to
oxygenate what may be deemed the real analogue of the blood, which
bathes every internal part of the body of an insect. Those animals likewise
that have a circulation are furnished with a liver, as is the case with the
Arachnida and even many aggregate animals that have a heart; but in
insects there are only hepatic ducts. M. Cuvier has also proved that the
conglomerate glands, which exist in all animals that have a heart and blood-
vessels, do not exist in insects, in which they are replaced by long slender
secretory tubes, which without being united float in the interior of the body:
from this circumstance, he is led to conclude that their nutrition is by
imbibition or immediate absorption, as in the Polypi and other zoophytes,
the chyle transpiring through the alimentary canal, and running uniformly to
all parts of the body[386].
These arguments appear so satisfactory, that Physiologists in general seem
to have been convinced by them that no circulation, at any time, takes place
in insects, and that their supposed heart is merely a secretory vessel, though
of what kind they were at a loss to conjecture[387]. But, convincing as they
seem, they appear to have been founded in error, and on the idea that a
circulation, as well as a heart, necessarily implies a vascular system
consisting of veins and arteries; for by the recent discoveries of M. Carus, it
has been satisfactorily proved that insects in their preparatory states, have
an extravascular circulation, the arterial and venose currents not being
confined by parietes. The observations upon which M. Carus' hypothesis is
founded, were made in the Autumn of 1826; and an abstract of their results
presented to the Union of German Naturalists and Physicians, which then
held its meeting at Dresden, many of the members of which, as MM. Oken,
Husche, Heyne, Purkinje, Otto, Weber, and Müller, had ocular proofs of the
reality of the phenomena.
His first observations were made on the larva of Agrion Puella, which
swims by means of three vertical laminæ attached to the tail; which, when
the wings first appear as rudiments, begin to be exsiccated and are finally
detached. Each of these laminæ, in its natural vertical position, presents an
inferior abdominal and a superior dorsal edge, has two tracheæ running
along its centre with ramifying bronchiæ, and consists of granular substance

contained between two strata of the external integuments. A current of
blood-globules enters each lamina somewhat nearer to its abdominal than to
its dorsal edge, and running through the greater part of its length suddenly
turns and bends its course back towards the body, somewhat nearer to the
dorsal than to the abdominal margin of the lamina. The channel thus formed
in the midst of the granular substance is perfectly transparent, except where
it is occupied by the blood-globules, or crossed by the bronchiæ. The
parietes of the channel are not strictly defined, nor formed by any thing like
the coats of a vessel, the blood circulating through the granular
Parenchyma; a circumstance however which is not peculiar to this case, but
also occurs generally in the first states of the circulation, as it presents itself
for instance in the embryo of Fishes, and in the figura venosa of the
incubated egg[394]. The blood-globules are elongated like a grain of wheat,
considerably larger than those of the human blood, and float in a fluid
which is invisible because of its transparency, but the existence of which is
proved by the variations in the position of the globules in the current,
sometimes following its direction, at others crossing it transversely, or more
or less obliquely.
When the animal is vigorous, the current is uninterrupted, although its
velocity is accelerated at regular intervals; and that not only in the excurrent
(arterial), but also in the recurrent (venous) part of its course through the
lamina. When the animal becomes exhausted, or the laminæ exsiccated, the
circulation is interrupted, and in the same manner, as under the same
circumstances, in the larvæ of frogs and lizards; the disturbance displaying
itself not merely by a cessation of the process, but also by retrograde
movements of the currents, or by oscillatory motions of the blood-globules.
In proportion as the wings are developed, the circulation in the laminæ
diminishes, and ultimately ceases, preparatory to the detachment of the
laminæ themselves. At the same time, however, it presents itself under a
new form in the wings. In these the excurrent or arterial stream takes its
course along the inner margin of the wing, and the recurrent or venous
returning along the outer; whilst, occasionally, other transverse currents
take their course through the net-work of the wing from its inner to its outer
margin. As the wings are further developed, the circulation in them, like
that in the caudal laminæ, gradually becomes weaker and ultimately
ceases[395].

The next observations were made on the transparent larva of a neuropterous
insect (probably a Semblis or Sialis), in which the pulsations of the dorsal
vessel were distinctly seen at its posterior extremity, from which they were
propagated towards the anterior; these two divisions of that vessel
appearing to bear to each other the relation of a heart and aorta. There were
no traces of other vessels, though regular and rapid currents of blood-
globules, exterior to the tracheæ, proceeded from the head towards the
posterior extremity of the body, where each of these currents entered the
heart, which again propelled its contents with accelerated velocity through
the anterior part of the dorsal vessel towards the head. The lateral currents
also were accelerated upon each contraction of the heart, proving that they
must communicate with the dorsal vessel at the anterior part of the body,
though the opacity of the head rendered it impossible to ascertain the mode
of anastomosis. An excurrent and returning current were also traced to each
of the legs[396]. But the phenomena of the circulation was most distinctly
visible in the larva of Ephemera vulgata, even more distinctly than it is
possible to trace it in the larvæ of frogs and newts. In this animal the
circulation, with the help of the microscope, is at once visible in the three
last segments of the body; and with a little attention is discoverable not only
in the three terminal caudulæ, and in the upper joints of the legs, but also in
the head, and particularly the roots of the antennæ. In the posterior part of
the body there are on each side two currents of blood, not bounded by
parietes, situate on each side of the intestinal canal, the inner one being the
most considerable. The external one communicates with the internal by
several intermediate branches; from this probably the streams are detached,
which in the form of loops are seen at the upper joints of the legs, though it
is not possible precisely to ascertain this, nor even whether these lateral
currents continue distinct in the thorax, which probably they do. At the
ninth abdominal segment these currents which flow posteriorly from the
head, change their direction, and are inflected so as to enter the pulsating
heart, from which the current again flows towards the head. Before they
enter the heart they give off three streams, one for each of the three
caudulæ. The currents in these caudulæ present the phenomena of the
circulation with peculiar distinctness, and are particularly remarkable from
the circumstance, that the excurrent and recurrent streams, though closely
approximated without any visible separation, flow without disturbing each
other. The excurrent stream is accelerated in correspondence with the

pulsations of the heart; the recurrent on the contrary being always
somewhat more sluggish, and the first to stagnate and cease when the
strength of the animal is impaired. In the anterior part of the head currents
can be discovered, forming loops like those of the legs, at the roots of the
antennæ; each current proceeding from the cranial surface, and in returning
taking its course towards the region of the larynx[397].
M. Carus has likewise observed currents of blood in the larvæ of water-
beetles (Hydrophilus and Dytiscus)[398]; but at present he appears to have
detected it in no terrestrial larva. Whether this is occasioned by their
opacity, or it exists only in the ovum, as he seems to suspect[399], must be
left for determination to future observers; it is scarcely probable, however,
that the larvæ of Dytisci and Hydrophili should differ from other Coleoptera
in their circulation.
The endeavours of M. Carus to discover any proofs of a circulation in
insects in their last state, except in the wings at their first development,
were without success[400]. He observes that the fact of the currents of fluids
in larvæ not being defined by vascular parietes, enables us to comprehend
the rapidity and facility with which the traces of the circulation are lost in
the perfect insect. On the other hand, that the existence of a circulation at
one period, and its cessation at another, elucidate many circumstances
connected with the physiology of these animals: for instance, the contrast
between the rapid growth and transformations of the larvæ, and the
stationary existence of the imago, &c. Lastly he remarks, that the
phenomena of this circulation do not throw any light on the obscure subject
of the mode of nutrition in perfect insects; which therefore must still be
supposed to be effected according to the idea of Cuvier, without the
intervention of vessels[401].
Whatever be the functions of the dorsal vessel, this seems the most proper
place to state to you what further is known respecting it. Its construction is
nearly alike in insects in all their states, except that in the imago it is shorter
and narrower. Reaumur has affirmed, and before him Malpighi made a
similar observation, that in chrysalises newly disclosed from the larva, and
yet transparent, the motion of the included fluid is the reverse of what it has
been in that state, it being propelled from the head to the tail, which he

found to be the case also in the imago[402]. If this be true, and there is no
reason to doubt his accuracy, when they are more advanced, it resumes its
old course, as Lyonet observed, from the tail to the head[403]. But probably
it is not always uniformly in the same direction, since Malpighi states that a
very slight cause will change its course, and that the pulsations differ in
quickness in different portions of the heart[404]. If its course were really
always the same, and in one direction, without any reflux, it would seem to
follow that the fluid must be absorbed at one end, and, if there was no
outlet, transpire at the other, which would be a kind of circulation. In
Syrphus Pyrastri and other aphidivorous flies, this dorsal vessel, instead of
the usual form which it had in the larva, assumes a very peculiar
appearance. If, taking one of these flies by the head and wings and holding
it up to the light, you survey under a lens the base of the lower part of its
abdomen, you will see through its transparent skin, which exactly forms
such a window as physicians have sometimes wished for in order to view
the interior of their patients, a flask-shaped vessel having its long end
directed towards the trunk, in which there is a manifest pulsation and
transmission of some fluid. This vessel extends in length from the junction
of the trunk with the abdomen to about the termination of the second
segment. The included fluid does not run in the dorsal vessel in a regular
course, but is propelled at intervals by drops, as if from a syringe, first from
the wide end towards the trunk, and then in the contrary direction, forming
a very interesting and agreeable spectacle. One circumstance led Reaumur
to conjecture that the neck of this vessel, which he at first regarded as
simple, is in fact composed of two or more approximated tubes, and that the
blood is conveyed forward by the outward ones, and backward by the
intermediate one[405]: he even thinks that he saw a kind of secondary heart,
at the extremity next the trunk, for the purpose of causing the reflux. This
illustrious author observed the above remarkable structure not only in the
Syrphi, but in many of their affinities, and thinks that it is also widely
diffused amongst the Muscidæ[406].
I must now say something upon what I conceive to be the real blood of
insects; for I think no one will object to that name being given to their
nutritive fluid, especially in the larva, though it does not circulate by means
of a vascular system. The chyle that is produced in the intestines of animals
from the food, is that fluid substance from which their blood is formed: in

insects it is not absorbed by the lacteals, but transpires through the pores of
the intestinal canal into the general cavity of the body, where, being
exposed to the influence of the oxygen in the air-vessels, it becomes, though
retaining its colour, a different fluid from what it was before, and analogous
to blood in its use and office[407]; only that in these animals, as Cuvier has
observed, at least in their perfect state, the blood, for want of a circulating
system, not being able to seek the air, the air goes to seek the blood[408].
The dispersion of this fluid appears to be universal, so that all the parts and
organs contain it in a greater or less degree[409]. In many insects, if you
break only an antenna or a leg, a drop of fluid flows out at the wound. In
larvæ, the fluid which bathes[410], or visits, all the internal parts and organs
is not only sufficient for their nutriment, but a large quantity of seemingly
superfluous blood remains that is not wanted for this purpose. This is
expended in the production of the caul or epiploon (Corps graisseux
Reaum.), which laps over and defends all the viscera of the animal, and
goes principally to the formation of the imago[411]. I have said that Cuvier
conceives nutrition in insects to take place by imbibition or immediate
absorption; that is, I suppose, the different parts and organs thus constantly
bathed in the blood, imbibe from it the particles necessary for their constant
accretion. M. Chabrier seems to think that it is the compression and
dilatation of the trunk that duly distributes the nutritive fluid[412]; Lyonet
compares the nutrition of insects by their fibres from this fluid, when
formed into the corps graisseux, to that of plants that draw their support by
their roots from the earth[413]. Much obscurity, however, at present rests
upon this subject—much for future investigation to explore; but in all the
works of the Most High there is always something inscrutable, something
beyond the reach of our senses and faculties, which teaches us humbly to
adore his infinite perfections.

II. The circulation of the Arachnida is next to be considered; and the term
applied to these becomes strictly proper. Two great tribes, in our view of the
subject, constitute this Class,—the spiders (Araneidea) and scorpions
(Scorpionidea): I shall give you some account of the circulating vessels of
each.—In spiders, the heart in general is a long dorsal vessel as in insects,
but supposed to be confined to the abdomen, growing slenderer towards
each extremity, particularly the anal. In some also, as in Aranea domestica,
like that of insects, it has lateral muscular appendages; but in others, as in
Clubiona atrox, it is without them[414]. It exhibits a pair of vessels that
appear to connect with the gills, by which the oxygenation of the blood
takes place, and a number of others that ramify minutely and are lost in the
analogue of the epiploon, supposed to be their liver[415]. Whether these last
are to be regarded merely as veins, has not been ascertained; they seem
rather to convey the blood outwards, than to return it back to the heart: but
this question must be left for future investigation. I may observe, however,
that though the heart of the spider has been traced only in the abdomen, it
may probably extend into the trunk.
The heart of the scorpion has been examined both by Treviranus and
Marcel de Serres; but I shall principally confine myself to the description of
the latter, as the most clear and intelligible. The heart, then, of these animals
is elongated, almost cylindrical, but attenuated at each end; it is extended
from the head to the extremity of the tail, and appears to have four pairs of
lateral muscles. On each side are four pairs of principal vessels, which go to
the pulmonary pouches, and there ramify. These may be assimilated to
veins. Besides these, there are four other vessels that cross them, forming
with them an acute angle, and which, with four branches of smaller size,
receive the blood from the pulmonary pouches, and distribute it to the
different parts of the body,—these are the arteries. Before it enters the tail,
the heart throws out two vascular branches which do not go to the gills, but
distributing the blood to different parts, ought to be considered as
arteries[416]. Treviranus mentions bunches of reticulated vessels, concerning
the use and origin of which he seems uncertain[417]; but as they approach
the gills they are probably the branching extremities of what M. de Serres
considers as the veins.
I am, &c.

LETTER XL.
INTERNAL ANATOMY AND PHYSIOLOGY OF INSECTS,
CONTINUED.
DIGESTION.

"The immense Class of insects," says the immortal Cuvier, "in the structure
of its alimentary canal exhibits as many variations as those of all the
vertebrate animals together: there are not only the differences that strike us
in going from family to family and from species to species; but one and the
same individual has often a canal quite different, according as we examine
it in its larva or imago state; and all these variations have relations very
exact, often easily estimable, with the temporary or constant mode of life of
the animals in which it is observable. Thus the voracious larvæ of the
Scarabæi and butterflies have intestines ten times as large as the winged
and sober insects—if I may use such an expression—to which they give
birth[418]."
In the natural families of these creatures, the same analogy takes place with
respect to this part that is observable in the rest of the Animal Kingdom; the
length and complication of the intestines are here, as in the other Classes,
often an index of a less substantial kind of nutriment; while their shortness
and slenderness indicate that the insect lives by prey[419].
In considering therefore the parts connected with the digestive functions of
the insect world, it will not be amiss to have reference to their food, and
their mode of taking it; but first it will be proper to state and define the parts
of this important organ.

In general the alimentary canal[420] is composed of the same essential
tunicks as that of the vertebrate animals, consisting of an interior epidermis,
a papillary and cellular tunick, and an exterior muscular one[421]. The first is
usually tender, smooth, and transparent; but not always discoverable,
perhaps on account of its tender substance[422]. Ramdohr does not notice the

papillary and cellular tunicks; they are probably synonymous with what he
denominates—the flocky layer (Die flockige lage), and which he describes,
when highly magnified, as appearing to consist of very minute globules or
dark points, and as being of a cellular structure[423]. The exterior tunick is
thicker and stronger than the interior, and composed of muscular fibres,
running either longitudinally, or transversely so as to form rings round the
canal. This tunick mostly begins at the mouth, and goes to the anus,
changing its conformation in different parts of the above intestine.
Sometimes however it originates only at the beginning of the stomach[424].
With respect to its general disposition, that canal—in its relative length, in
the size of its different parts, in the number and form of its dilatations, and
particularly of its stomachs and its cœcums, and in the folds of its interior—
exhibits variations altogether analogous to those of vertebrate animals, and
which produce similar effects[425]. As to its parts, it may be considered as
consisting of two larger portions, between which the biliary or hepatic
vessels form the point of separation. In the first, the most universal parts are
the gullet and the stomach; and in the second, the small intestine and the
large intestine[426].

1. The gullet (Œsophagus[427]) is that portion of the intestinal canal which,
receiving the food from the pharynx, or immediately from the mouth,
conveys it to the stomach. Though it often ends just behind the head[428], it
is usually continued through the trunk, and sometimes even extends into the
middle of the abdomen[429]; it therefore seldom much exceeds in length half
the body. It is constantly long when the head is connected with the trunk by
a narrow canal—as in the Hymenoptera, Neuroptera, Lepidoptera, &c.; but
is frequently short when these parts are more intimately united[430]. It often
ends in a kind of sac analogous to the crop of birds. Under this head I must
mention a part discovered by Ramdohr, which he calls the food-bag
(Speisesack), as he thinks, peculiar to Diptera[431]. From the mouth in these
proceeds a narrow tube into the abdomen, where it expands into a blind sac
having no connexion with the stomach; so that the fluid food, as blood, &c.
stored in it, must be regurgitated into the mouth before it can pass into that
organ[432]. Thus these animals, besides their stomach, have a reservoir in
which to store up their food; the product therefore of a single meal will
require several days to digest it.

2. The stomach (Ventriculus[433]) is that part of the intestinal canal
immediately above the bile-vessels, which receives the food from the gullet
for digestion, and transmits it when digested to the lower intestines[434]. By
its admixture with the gastric juice, the food acquires in the stomach a quite
different colour from what it had in the gullet. In herbivorous insects it
contains no acid, but, like the gastric juice of herbivorous quadrupeds, is of
an alkaline nature[435]. The chyle is forced through this organ, probably in
part by the pressure of the muscular fibres during the peristaltic motion; and
being pressed through the inner skin, is first collected in the intermediate
cellular part, and ultimately forced through the outer skin[436]. At its
posterior end it terminates in the pylorus, a fleshy ring or sphincter formed
of annular muscular fibres[437]. The stomach often consists of two or more
successive divisions, which are separated from each other, and are often of
an entirely different conformation and shape[438]. In the Orthoptera,
Predaceous Coleoptera, and several other insects, an organ of this kind
precedes the ordinary stomach, which from its structure Cuvier
denominates a second stomach or gizzard[439]; Posselt improperly calls it
Cardia[440]; and by Ramdohr it is named the plaited-stomach (Falten-
magen[441]). It is a short fleshy part consisting of two skins, placed above
the opening of the stomach, and perhaps rather belongs to the gullet. The
inner skin is formed into longitudinal folds, and sometimes armed with
horns, teeth, or bristles. Its cavity is very small and compressed, so as to
admit only small masses of food, and yet present them to a wide surface for
the action of the teeth or bristles;—in this stomach therefore, as in the
gizzard of birds, to which it seems clearly analogous[442], the food is more
effectually comminuted and rendered fit for digestion. The muscles, by
which its action upon the food is supported, in some species amount to
many thousands[443]. Rudiments of a gizzard are sometimes found
concealed in the gullet of many insects[444]. The idea of Swammerdam,
Cuvier, &c. that grasshoppers and other insects that have this kind of
stomach, chew the cud[445], Ramdohr affirms is entirely erroneous[446].
Besides its divisions, the stomach has other appendages that require notice.
In most Orthoptera, a pair or more of blind intestines or cœca may be found
at the point of union of the gizzard with the stomach[447], which have been
regarded as forming a third stomach: they also begin the stomach in the

louse[448]; they form a coronet round the apex of that organ, in the grub of
the cockchafer[449]; and in that of the rose-beetle, there is one at the apex,
one in the middle, and a third at the base[450]. Besides these appendages,
which are formed of the skin of the stomach, there are others that are not so.
In the Predaceous and some other beetles, the whole external surface of this
organ is covered with small blind appendages opening into the space
between its two skins, which cause it to resemble a shaggy cloth; these
Ramdohr calls shags (zotte[451]), and Cuvier, hairs[452] (villi). These
appendages the latter author seems to regard as organs that secrete the
gastric juice and render it to the stomach[453]; but the former thinks their use
uncertain[454].
3. The small intestines (Intestina parva) are the portion of intestines next
the stomach, and consist often of three distinct canals;—the first is
supposed to be analogous to the duodenum; it is found only in the
Coleopterous genera Silpha L. and Lampyris L., and is distinguished from
the succeeding intestine by being perfectly smooth[455]. Next follows the
thin intestine (Dünndarm), which in the above insects is wrinkled; it most
commonly immediately follows the stomach. Sometimes it is wholly
wanting, as in Agrion, the Hemiptera[456], &c. Ramdohr conjectures that it
is not solely destined for conveying the excrement, but that probably some
juices are separated in it from the food especially for the nutrition of the
gall-vessels, as their principal convolutions are mostly near this
intestine[457]; which perhaps may in some cases be regarded as analogous to
the jejunum in vertebrate animals. The third pair of the small intestines,
which perhaps represents the ileum, Ramdohr distinguishes by the name of
club-shaped (Keulförmigen Darm[458]). It may generally be regarded as
only a continuation of the former thickened at the end so as to resemble a
club reversed. It is however sometimes separated from the thin intestine, as
in Cerambyx moschatus[459].
4. The large intestines (Intestina magna) consist sometimes of two portions.
The thick intestine (Dicken-darm), which may be regarded as a kind of
cœcum, is found only in the larvæ of the Lamellicorn beetles, but never in
the perfect insect. In shape it is oval and folded; whence it is thicker than
the rest of the intestinal canal, and is constantly filled with excrement[460].

The second portion of these intestines is the rectum (Mastdarm), which
terminates in the anal passage. This part is scarcely ever wanting, except
when the insect evacuates no excrement, which is the case with the grubs of
bees, wasps, and the antlion (Myrmeleon). In the imago of Telephorus, at
least in T. fuscus, it is also obsolete[461]: in most cases, however, it is very
distinct from the preceding intestine. Sometimes it consists of only one
tunick composed of muscular fibres[462]. When the gullet is wide, the
rectum is usually so likewise; but when it follows a club-shaped or thick
intestine, it is narrow[463]. It generally may be termed short[464]. When
wide, it often contains a great quantity of excrement, as the gullet does of
undigested food; but when narrow, the excrement seldom remains long in it.
This intestine also in a few cases has a lateral enlargement or cœcum (Blind-
darm), being a continuation of the same skin; but perhaps this enlargement
is really analogous to what Ramdohr calls the thick intestine, though in
these cases he regards it as an appendage of the rectum[465].
I must now call your attention to the bile-vessels of insects. These, by
Malpighi[466] and the earlier physiologists, who regarded them as a kind of
lacteals, were denominated varicose vessels: but Cuvier—and his opinion
after some hesitation has been adopted by Ramdohr—considers them as
vessels for the secretion of bile, and as analogous to the liver of animals that
have a circulation[467]. As the want of blood-vessels prevents insects from
having any gland, the bile is produced with them, as all their other
secretions, by slender vessels that float in their nutritive fluid, and from
thence secrete the elements proper to form that important product, which
usually tinges them with its own yellow hue; though in the Lamellicorns
and Capricorns they are of an opaque white, and in the Dytisci of a deep
brown colour[468]. Their bitter taste further proves that they contain the
bile[469]. They are long, slender, filiform, tortuous or convoluted, and
mostly simple vessels; sometimes gradually smaller toward the base[470], at
others towards the apex[471]. In some, screw-shaped[472]: in one larva, with
hemispherical elevations[473]: in the cockchafer, part of them are fringed on
each side with an infinity of short, blind, minute, setiform tubes, while the
rest are naked[474]; they are composed of a single, thin, transparent
membrane, according to Ramdohr[475]; but Cuvier thinks their texture is
spongy[476]. They appear to contain a number of small, irregular, dark

granules, which float in a peculiar fluid, with which, however, they are not
always filled throughout, nor are they constantly permeable from one end to
the other. Thus in the meal-worm beetle (Tenebrio Molitor), the common
trunk by which they are attached to the intestinal canal is composed of
gelatinous granules[477]. The place of their insertion is generally a little
below the pylorus, but in the common cockroach they are inserted into the
stomach just above that part[478]. Usually each vessel opens singly into the
intestinal canal, which the whole number surround at an equal distance
from each other[479]. Sometimes, however, they are connected with it by a
common tube in which they all unite, as in the asparagus-beetle (Lema
Asparagi[480]), and the mole-cricket (Gryllotalpa vulgaris[481]); in the
house-fly (Musca domestica), and other Muscidæ, each pair unites so as to
form a single branch on each side of the canal previously to their
insertion[482]; in the field-cricket (Gryllus campestris) they are all inserted
in one spot[483]; and when numerous, they are generally attached singly
though irregularly[484]. These vessels at their base do not open into the
cavity of the intestinal canal, but merely into the space between its outer
and inner tunicks, the last being constantly imperforated[485].
With regard to their apex, the bile-vessels are sometimes fixed singly or
connectedly to the intestine merely by a few muscular fibres; for they do
not enter it, their ends having no orifice. This structure is mostly to be met
with in the Coleoptera[486]. In caterpillars, the tops of these vessels
perforate the outer skin of the rectum, and proceeding in dense convolutions
to the anus, become at last so fine that their terminations cannot be
discovered[487]. In other cases, the extremities of a pair of these vessels
unite so as to form a double one: this may be seen in those of Philonthus
politus[488], and probably other rove-beetles: and lastly, in others the bile-
vessels are free, hanging down by the intestinal canal, without being
attached to it or to each other. This structure is constantly found in the
Orthoptera and Hymenoptera Orders, &c.[489].
With regard to their number, the bile-vessels vary from two to upwards of
one hundred and fifty, yet so that their whole amount is constantly the
product of the number two,—at least as far as they have been counted: and
even when those on one side are not alike, a similar variation takes place in

the other, as may be seen in Galleruca Vitellinæ, where on each side are two
long ones and one shorter[490]; the most usual numbers are, four—six—or
many, that is, more than twenty—

Two bile-vessels are found
the larva of Cetonia aurata[491].
in
most Coleoptera, Diptera, and
Four
Hemiptera[492].
Six Lepidoptera, some Coleoptera[493], &c.
Eight Myrmeleon, Hemerobius[494].
Fourteen Formica rufa[495].
Twenty larva of Clavellaria Amerinæ[496].
Libellulina, Orthoptera, and
Many
Hymenoptera[497].

The bile-vessels vary considerably in length: in many cases where they are
free they are short[498]; they are often very long, and perhaps those that are
fixed may be generally stated as the longest. In the Lamellicorn beetles they
are remarkable for their great length[499].
Having given you this general account of the intestinal canal and its parts
and appendages, I shall now state some of the peculiarities that in this
respect distinguish particular tribes and families.
The Coleoptera alone, exhibit as many variations in the structure of the
alimentary tube as all the other Orders of insects together:—to particularize
these would occupy too large a portion of this letter, I shall therefore only
notice a few of the most remarkable. In general they may be stated as
having universally a stomach, a small intestine and rectum, and not more
than three pairs of fixed or united bile-vessels. In the Predaceous beetles,
the gullet mostly widens at the base into a considerable crop, followed by a
gizzard, a shaggy stomach, and two pairs of united bile-vessels. The whole
alimentary canal in these, is never less than double, and sometimes treble
the length of the body[500]. In the carnivorous beetles, at least the
Staphylinidæ and Silphidæ, there is little or no crop, and the gizzard is
hidden: in the former, the whole length of the intestinal canal is not twice,

while in the latter it is more than four times that of the body[501]. In these
also the intermediate portion of the large intestine is singularly
annulated[502]. In the Petalocera the stomach is usually longer than all the
rest of the intestines together, and often convoluted: in the cockchafer the
whole intestinal canal is nearly five times the length of the body, four parts
of which is occupied by the stomach[503]. In the grub the canal scarcely
exceeds the length of the animal[504]. In Lampyris the stomach exhibits a
remarkable appearance, having on each side a series of spherical folds or
vesicles[505]. Have these any thing to do with the secretion of its phosphoric
matter? Tenebrio has a gizzard armed internally with calluses, and a shaggy
stomach, and Blaps does not differ materially; their entire canal is more
than twice the length of the body[506]. In the vesicatory beetles (Cantharis,
Meloe, &c.) there is no gizzard, and the canal is less than twice the length of
the body[507]. Little is known with regard to the alimentary canal of the
beetles distinguished by a rostrum (Rhyncophora). In the only two that
appear to have been examined, Rhynchites Betuleti and Cryptorhynchus
Lapathi, that canal is moderately long, the stomach partially shaggy, and the
small intestine inversely claviform; but in other respects they differ
materially[508]. In the former there is no crop or gizzard, the stomach is
fringed on each side, except at its upper extremity, with a series of small
cœca or shags, and there are three pairs of bile-vessels[509]; while in the
latter the gullet is dilated into a crop which includes a gizzard in which the
skill of a Divine artist is singularly conspicuous:—though so minute as
scarcely to exceed a large pin's head in size, it is stated to be armed
internally with more than 400 pairs of teeth, moved by an infinitely greater
number of muscles[510]. A transverse section of this gizzard represents two
concentric stars, with nine rays each[511]: the object of this structure is, the
comminution of the timber which this beetle has to perforate and probably
devour[512]. The stomach is very slender, but dilates in the middle into a
spherical vesicle[513], and there are only two pairs of bile-vessels[514]. In the
Capricorn beetles, the part we are considering varies much: in general we
may observe that it is more than double the length of the body, that the
stomach is long and slender, and usually naked, that the gullet terminates in
a crop without a distinct gizzard, and that there are three pairs of bile-
vessels[515]. In the Herbivorous beetles (Chrysomela, Cassida, &c.) the

canal is more than double the length of the body, and in some much
longer[516], the stomach is long, and commonly naked; but in Chrysomela
violacea it is covered with hemispherical prominences[517], and in
Chrysomela Populi it is shaggy[518]; in the insect last named and Galleruca
Vitellinæ the rectum consists of two pieces[519]. In this tribe the intestines of
the larva resemble those of the perfect insect[520].
In the Orthoptera the alimentary canal, which continues the same in every
state, is short, or only moderately long; the gullet has one or two lateral
pouches or crops[521], and terminates in a gizzard of curious construction,
with singular folds and teeth[522]; then follows a short stomach, usually with
a pair or more of cœca at its upper extremity[523]; the lower intestines are
not distinct, and the bile-vessels numerous, short and free[524].
In the Neuroptera, many of the genera are distinguished by the remarkable
length of the gullet, and by the lower intestines forming one short piece[525].
In the Libellulina the bile-vessels are numerous, short, and free, as in the
Orthoptera[526]. In Hemerobius and Myrmeleon there is a gizzard[527], and
just above it a cœcum, in the former very remarkable, is connected with the
gullet[528].
The Hymenoptera appear all to be distinguished by a long slender gullet,
terminating in a dilated crop forming the honey-bag; their stomach is
variable, their small intestine slender, and the rectum dilated;—their bile-
vessels, like those of the two preceding Orders, are numerous, short, and
free[529]. In the ants and ichneumons there is an approach to a gizzard[530].
In the wasp and humble-bee the stomach is very long, with muscular rings
surrounding it[531]. In this Order the larvæ at first have no lower intestines
and void no excrement[532], but as they approach to the pupa state one
begins to appear[533].
The next insects whose alimentary canal we are to consider, are those
which, taking their food by suction, have no occasion for masticating
organs: this may in part be predicated of the preceding Order, in which most
of the tribes in their perfect state imbibe fluid food, and use the ordinary
organs of mastication principally in operations connected with their
economy; and their crop, in which the honey in many is stored up for

regurgitation, may be regarded in some degree as analogous to the food-bag
of the Diptera and other suctorious insects.
The two sections of the Hemiptera Order differ widely in the canal we are
considering, and I shall therefore give a separate account of each. In the
Heteropterous section, appended to the gullet by a long convoluted
capillary tube, besides the usual saliva-reservoirs there is often a double
vessel, which Ramdohr regards as discharging the same function, but which
in many respects seems rather analogous to the food-reservoir of the
Diptera[534]. As I have had no opportunity of examining this vessel, I shall
content myself with stating this idea, and describe the vessel more fully
hereafter. The gullet, in these, usually terminates in an ample crop
consisting of many folds[535], followed by a long, slender, cylindrical tube,
dilated at its base into a spherical tumour; these two may be said to form the
first stomach: to this succeeds a second[536], which Ramdohr denominates
the bug-stomach (Wanzen-magen), which varies in its figure, and in
Pentatoma consists of four demi-tubes, so as to form a quadrangular
canal[537]. In the Homopterous section of this Order Ramdohr seems to have
examined but few; Chermes however and Aphis exhibit one remarkable
feature; they have no bile-vessels, at least he could discover no trace of
these organs[538]. Their intestinal canal is very simple, their stomach very
long, widest above, and somewhat convoluted, with a very slender
gullet[539]. In Cercopis spumaria the structure is more complex, and
extremely singular. It has two or rather three stomachs; the two first of a
horny substance, and the last a slender somewhat convoluted membranous
tube, which becoming reversed, is attached by what should be deemed its
lower extremity to the first stomach, from the other side of which emerge
the lower intestines, terminating in a thick pear-shaped rectum. At the same
point of the first stomach the four bile-vessels are attached, they grow
gradually thicker for about a third of their length, when they become
twisted like a cord, and taper towards the rectum, to which also they are
attached[540]. From this structure it should seem that the food has to pass
twice through the first stomach, before the process of digestion is complete,
and it is rejected at the anus.
The next suctorious Order is the Lepidoptera: in these the gullet is long and
slender, surrounded at the beginning with a loose transparent skin, and at

the base furnished with a pair of lateral sacs, forming the honey-stomach,
and probably analogous to the food-reservoirs of the Diptera, which when
blown up are of an oval form; the stomach, as in the bugs, consists of two
portions, the first being the longest[541]. There are three free bile-vessels on
each side, proceeding from a single branch[542]. It will not be uninteresting
here to abstract from Herold the progressive changes which take place in
the intestinal canal in this Order, during the transition of the animal from
the larva to the imago state. In the larva, the gullet, the small intestine, and
the rectum, are short and thick[543], there are a pair of silk reservoirs
(sericteria), as well as vessels for the secretion of saliva (sialisteria): if you
examine it two days after its first change, you will find the gullet and the
small intestine much lengthened and become very slender; the stomach
contracted both in length and size; the rectum also changed, and the silk
vessels contracted[544]. These in a pupa eight days old have wholly
disappeared; the gullet is become still longer, its base is dilated into a crop
or food-reservoir; the stomach is still more contracted, and instead of a
cylinder represents a spindle; the small intestine also is lengthened[545]: at a
still more advanced period, when it is near appearing under its last form, the
gullet and small intestine are still more drawn out; and the honey-bag,
though very minute, has become a lateral appendage of the gullet[546]; and
lastly, in the butterfly it appears as a large vesicle[547]; the small intestine is
grown very long[548]; and the rectum has changed its form and acquired a
cœcum[549]. When we consider the adaptation of all these changes of form,
the loss of old organs and the acquisition of new ones, to the new functions
and mode of life of the animal, we see evidently the all-powerful hand of
that Almighty Being who created the universe, upholding by his
providence, and the law that he has given to every creature, the system that
he at first brought into existence.
We now come to the Diptera. These have a very slender gullet, to which is
attached on one side a long filiform tube, terminating in the food-reservoir,
which in some instances is simple[550], but most generally consists of two or
more vessels[551], collapsing when empty, but varying in shape and size
when inflated with food: the mouth of the stomach in many cases is dilated
into a kind of ring[552]; sometimes there is on each side a blind appendage
or cœcum opening into it, in Bombylius covered with shags, which though

not connected with the mouth by a tube, Ramdohr regards as saliva-
reservoirs[553]; in Musca vomitoria the beginning of this organ below the
mouth is covered with hemispherical prominences, and in Tipula it is
dilated and marked with transverse folds. There are usually two pairs of
bile-vessels; in the Muscidæ pedunculate and free[554]; in Tipula,
Bombylius, and Leptis, sessile and united[555]; and in Tabanus sessile and
fixed[556]. It is remarkable that in some of this Order—the reverse of what
usually happens—the alimentary canal appears to be much longer in the
larva than it is in the imago; in Musca vomitoria, its length in the former is
two inches and a quarter, while in the latter it is only one inch and one
third[557]. A singular organ distinguishes the imago of this species, the use
of which appears not to be discovered. It succeeds the rectum, and has on
each side two short club-shaped appendages, open at the end, which receive
tracheæ, and terminate in a short piece that opens into the anus[558].
In Hippobosca and its affinities the canal in question differs from that of
other Diptera, in having no food-reservoir; in other respects it resembles
it[559].
From the above statement it appears that the principal character which
distinguishes those that take their food by suction, from those that masticate
it, is the faculty with which they are furnished by means of an ample crop,
honey-stomach, or food-reservoir, of regurgitating the food they may have
stored up. Another distinction still more striking, which will appear more
evidently hereafter, is to be seen in the saliva-secretors with which the
suctorious tribes are furnished, to be found in very few masticators, by
which they are enabled to render the juices more fluid and fit for suction.
The only insect amongst the Aptera whose alimentary canal I shall notice, is
the common harvest-man (Phalangium Opilio): in this, though the stomach
and lower intestine are remarkably simple, yet their cœcal appendages are
numerous and singular: the former, which has no distinct gullet, is pear-
shaped[560]; and the latter, tapering downwards, and truncated at the
end[561]; connected with it above are no less than twenty-three cœca or
blind appendages, of various forms and dimensions; the last pair but one of
which is very remarkable, being bent like a bow, and furnished externally

with four short clavate processes[562]. It is probable that some of these
organs are analogous to the bile-vessels of other insects.

When the Creator in his wisdom fixed the limits of the various tribes of
animals, he united them all into one harmonious system by means of certain
intermediate forms, exhibiting characters taken some from those that were
to precede, and others from those that were to follow them, and this not
only in their external structure, but likewise in their internal organization;
so that we are not to wonder if in the same individual we meet with organs
that belong to two distinct tribes, or if, remaining nearly the same in their
prima facie appearance, they begin to exercise new functions. An instance
of this we have seen in the dorsal vessel of insects, which in the Arachnida,
though not materially different in situation or general form, by the addition
of a small apparatus of arteries and veins becomes the centre and fountain
of a regular system of circulation[563]. From the circumstances here alluded
to, physiologists have been led to entertain very different sentiments with
regard to the structure of the alimentary organs of the Class we are now to
enter upon, the Arachnida: what some regard as a real liver, others look
upon as an epiploon or caul; and what the last denominate bile-vessels are
by some of the former considered as appropriated to the secretion of
chyle[564]. Yet both these opinions have some foundation in nature. When,
in the Arachnida, we discover a lobular substance consisting of granules
filling the whole cavity of the body and wrapped round the intestines, every
one will see in it no small analogy to the epiploon which in insects performs
the same function: but when, upon a further examination, we detect certain
vessels communicating with this substance and the intestinal canal[565], the
idea that these may be hepatic ducts, and this substance analogous to the
liver, immediately strikes us as not improbable. Again: when we discover
pairs of other capillary and tortuous vessels connecting with the intestinal
canal either at the pylorus[566] or below it[567], which in appearance
strikingly resemble the bile-vessels which we so constantly find in insects,
we seem warranted in concluding that they are of the same nature and use:

but when a nearer inspection enables us to detect the hepatic ducts just
mentioned in the scorpion, and we find that these capillary vessels in the
spider are in a very different situation from those in insects which we
suppose them to represent, it occurs to us as not unlikely, that their function
may be different.
Let us now consider how the intestinal canal is circumstanced in the two
sections into which the Class Arachnida is divided; the Scorpionidea, and
Araneidea. In the Scorpions, this organ proceeds from the mouth to the anus
without any flexure or convolution, so that its length is scarcely equal to
that of the body[568]; it is slender, and its diameter, with the exception of an
irregular dilatation here and there, is nearly the same in its whole extent; the
gullet is short; the stomach long, and nearly cylindrical; the duodenum
shorter and thicker than the stomach, from which, as well as from the
rectum, it is separated by a valve; the latter is cylindrical, and opens at the
anus above the insertion of the vesicle that secretes the poison[569]. With
regard to the biliary system and its organs: The liver is of a pulpy granular
consistence and of a brownish colour, fills the whole cavity of the trunk and
abdomen, and serves as a bed for the other intestines. It is divided
longitudinally into two portions, by the channel in which the heart reposes
—its anterior part is formed into many irregular lobes, by the sinuosities of
the trunk; at the other extremity, it terminates in two acute ends, which enter
the first joint of the tail; its surface presents a reticular appearance, the
result of the approximation of polygonous lobuli; its interior is a tissue of
infinitely minute glands: in Scorpio occitanus there are about forty
pyramidal lobuli detached from each other, the summits of which, by their
union, form bunches that have their excretory canals, varying in number in
different species, which convey the bile to the alimentary tube; in the above
insect there are six pairs, three in the trunk and three in the abdomen, and in
S. Europæus a smaller number[570]; these vessels run transversely from the
liver, or aggregation of conglomerate glands, to the intestinal canal[571]; the
bunches consist of an infinite number of spherical glands, generally filled
with a brown thick fluid[572]: besides the transverse vessels, from the base
of the stomach there issue two pairs of very slender tortuous ones,
seemingly analogous to the common bile-vessels; one pair of which runs
upwards, one on each side that organ towards the mouth, forming here and
there some ramifications which enter the liver; and the other runs nearly

transversely to it[573]. As the fluid contained in these vessels is different
from that contained in the glands of the liver, M. Marcel de Serres supposes
they may be chyliferous[574].
In the Araneidea also the alimentary canal is nearly straight, and scarcely
exceeds the length of the body: the gullet is rather thick and cylindrical[575];
the stomach is distinguished anteriorly by two pairs of sacs, the upper pair
being much the largest and nearly triangular, the lower linear[576]; from
these sacs a narrow tube runs towards the rectum, but which is so entangled
with the liver, muscles, &c., as not to be easily made out[577]; the rectum is
rather tumid, and has a lateral cœcum[578]. The disposition of the liver or
conglomerate glands is stated to be similar to that of the scorpion[579]; it is
usually white, but in some species it is yellowish, or reddish, and its lower
surface has sometimes regular excavations[580]; no transverse hepatic ducts
connecting it with the alimentary canal, as in the scorpion, appear to have
been at present discovered: two pairs of capillary free vessels are attached
to the base of the rectum on one side, which, except in their situation, seem
analogous to the bile-vessels of insects[581].
From the above detailed account of the alimentary canal of the animals
whose internal anatomy we are considering, it appears that M. Cuvier's
observation—that the length and complication of the intestines indicate a
less substantial kind of nutriment—does not hold universally: thus, in
Necrophorus and Silpha, carnivorous insects, the intestinal canal in its
length and convolutions exceeds those of most herbivorous ones, and in
Cassida viridis and some others of the latter tribe are not longer than those
of the predaceous beetles. In herbivorous larvæ also, in general, the length
of the alimentary canal does not exceed that of the body, but in those of
some flesh-flies (Musca vomitoria) it very greatly exceeds it[582]. So true is
the observation—that there is no general rule without exceptions.
In this letter it may not be out of place to say a few words upon the
excrements of insects; which, strange as the observation may seem, but it is
no less true than strange, are sometimes pleasing to the eye, from their
symmetry, and to the taste, from their sweetness. In those that masticate
their food they are solid, and in those that take it by suction, fluid or semi-
fluid. In the caterpillars of Lepidoptera they are of the former description,

and every grain wears some resemblance to an insect's egg: as the passage
in many of these consists of six fleshy parts separated by channels, so the
excrement represents six little prisms separated by six channels[583]. The
Aphides all secrete a fluid excrement as sweet as honey, of which the ants
are so fond[584], which is ejected not only at the anal passage, but, in many,
by two little siphonets also above it[585]. A semi-fluid excrement is
produced by some species of Chermes, as that which inhabits the Box,
which often comes from the animal in long convoluted strings resembling
vermicelli. Reaumur says its taste is agreeable, much more so than that of
manna[586]. Under this head should be included the abundant spume with
which the larva of Cercopis spumaria envelopes itself[587].
I am, &c.

LETTER XLI.
INTERNAL ANATOMY AND PHYSIOLOGY OF INSECTS,
CONTINUED.
SECRETION.

Having given you so full an account of the system of digestion in insects, I
am now to say something concerning their secretions, and the organs by
which they are elaborated. Though no individual amongst them perhaps
secretes so many different substances as the warm-blooded animals; yet in
general the Class abounds in secretions perhaps as numerous and
extraordinary as in the last-mentioned tribes, to some of which a few of
them are analogous, while others are altogether peculiar. We know little or
nothing of the mode in which the process of secretion in insects is
accomplished; in most cases we cannot even discover, except in general,
whence the secreted substance originates; and in others, though we are able
to trace the vessels that contain it, we are often in the dark as to their
structure.—Cuvier, as has been before hinted, from not being able to detect
any thing in them like glands, and from their being constantly bathed in the
blood or nutritive fluid, conceives that they separate the peculiar substances
they contain, by imbibition or infiltration, through the pores of the skin[588];
a circumstance which seems to indicate a certain conformation of the pores
both as to size and figure, so as to enable them to admit only one peculiar
product.
In treating on this subject, I shall first consider the organs of secretion, and
next their products.
I. Organs of Secretion. In general, these are membranous vessels that float
in the blood or nutritive fluid, and secrete from it a peculiar substance. They
may be denominated according to their products—Silk-secretors, Saliva-
secretors, Varnish-secretor, Jelly or Gluten-secretor, Poison-secretor, and
Scent-secretors.

i. Silk-Secretors (Sericteria). These organs are most remarkable in the
caterpillars of the nocturnal Lepidoptera or moths, especially in that tribe
called Bombyces, to which the silkworm belongs: but this faculty is not
confined to these insects, but is shared by many other larvæ in different
Orders; and in one instance at least, by the imago. In general, the outlet of
the silk-secretors is at the mouth; sometimes, however, as in the larva of
Myrmeleon and the imago of Hydrophilus, its exit is at the anus. The first is
the organ which in the silk-worm provides for us that beautiful substance
from which the animal takes its name. There are always two of these
vessels, which are long floating tubes, growing slender towards the head of
the insect, where they unite to form the spinneret (fusulus) before
described[589], which renders the silk. Their lower extremity also is
commonly more slender than the middle, and is closed at the end. These
organs are usually very much convoluted and twisted[590]. According to
Ramdohr[591], they consist of two transparent membranes, between which is
found a yellow or transparent jelly. The greater the quantity of silk
employed by the caterpillar in the construction of its cocoon, &c., the
longer are the silk-secretors. Those of the silkworm are a foot long[592],
while those of the larva of the goat-moth are little more than three
inches[593].
Other insects spin silk with the posterior extremity of their body. In the
great water-beetle (Hydrophilus piceus) the anus is furnished with two
spinnerets, with which it spins its egg-pouch[594]; these are in connexion,
probably, with the five long and large vessels containing a green fluid,
described by Cuvier[595], which surround the base of each branch of the
ovaries. The larva of Myrmeleon, which also spins a cocoon with its anus,
differs remarkably in this respect from other insects, since its reservoir for
the matter of silk is the rectum; this is connected with a horny tube, which
the animal can protrude, and thus agglutinate the silk and grains of sand that
compose its cocoon[596].
The web of spiders is also a kind of silk remarkable for its lightness and
extreme tenuity. It is spun from four anal spinnerets, which never vary in
number; two longer organs peculiar to some species have been mistaken for
additional ones, but Treviranus affirms that they are merely a kind of anal
feeler. Their structure, as far as known, has been before described[597]. The

web is secreted in vessels varying in form. In some (Clubiona atrox) they
consist of two larger and two smaller ones, at the base of which lie many
still more minute[598]. The four larger vessels are wide in the middle,
branching at top, and below terminating in a narrow canal leading to the
spinnerets[599]. Treviranus thinks the fluid contained in the lower minute
vessels different from that furnished by the larger ones—but for what
purpose it is employed has not been ascertained.
ii. Saliva-secretors (Sialisteria). These are organs, rendering a fluid to the
mouth or stomach, that are found in many insects, especially those that take
their food by suction, as the Hemiptera, Lepidoptera, and Diptera, though
they are not confined to the perfect insect, being also in some cases visible
in the larva. Swammerdam was one of the first that discovered them, and he
suspects that they may be salival vessels; though he, as well as Ramdohr,
thinks they are the same with the silk vessels of the caterpillar[600]; an
opinion which Herold has sufficiently disproved, by showing that at one
period of the insect's life they co-exist[601], and Lyonet discovered a very
conspicuous pair in the caterpillar of the Cossus, co-existent with the silk-
secretors[602]. But the physiologist who has given the fullest account of
these organs is Ramdohr:—I shall therefore extract chiefly from him what I
have further to communicate with respect to them.
They are variously constructed blind vessels, that are present in almost all
insects that take their food by suction, but are mostly wanting in those that
masticate it. They have been found, however, in Cryptorhynchus Lapathi,
Chrysopa Perla, and Iulus terrestris. The most usual number of the saliva-
secretors is two[603]; but sometimes, as in the first of the last-named insects,
there is only one[604]; in others (Pentatoma Baccarum) there are three, the
exterior one consisting of a pair of reservoirs connecting with the gullet by
a single capillary tube[605]; in Pentatoma prasina there appear to be
four[606]; in Nepa cinerea, even six—the exterior double pair in this insect,
under a powerful lens, is found to consist of spherical vesicles, resembling
somewhat a bunch of currants[607]; and in Syrphus arcuatus they are
covered with four rows of similar ones[608]. In the flea they consist of two
pair of spherical reservoirs, each of which is connected with a short tube,
which uniting with that of the other forms a common capillary one

connecting with the mouth or gullet[609]; these organs sometimes terminate
below in slender vessels;—thus, in Nepa, the inner pair terminates in a
single vessel of this description[610], and in Tabanus and Hemerobius
apparently in many[611]. It admits of a doubt however, as was lately
observed, whether in the Hemiptera, which have usually more than a pair
of these organs, some are not rather food-reservoirs as in the Diptera.
The saliva-secretors open either into the instruments of suction themselves
(Tabanus, Musca); or into the entrance of the gullet (Pentatoma, &c.); or,
lastly, into that of the stomach (Syrphus, Bombylius). Those which lie at the
entrance of the stomach consist only of a blind uniform tube[612]; but there
is commonly to be distinguished in those that open into the mouth, a
reservoir, varying in shape in different species, and terminating in a
capillary tube, or tubes, at one or both extremities[613]. In Bugs, two pair of
these vessels are often present, one of which opens into the stomach
(Reduvius), or gullet (Pentatoma), but the other into the instruments of
suction[614]. In the Diptera they open into the stomach when the insect feeds
only upon the nectar of flowers (Syrphus), and into the proboscis when it
feeds upon both animal and vegetable juices (Tabanus, Musca). The
function of the fluid secreted by these organs is to moisten or dilute the food
before it is received by the instruments of suction and passed to the
stomach[615]. When a common house-fly applies its proboscis to a piece of
sugar, it is easy to see that it moistens and dissolves it by some fluid.
iii. Varnish-secretor (Colleterium). In butterflies, moths, and several other
insects, one or more vessels called blind vessels open into the oviduct,
concerning the use of which, physiologists are not agreed. In the cabbage
butterfly there is a pair of ovate ones, or rather a bilobed one, each lobe of
which externally terminates in long perplexed convolutions, not easily
traced, filled with a yellow fluid, which Reaumur and Herold think is used
for varnishing or gumming the eggs, so that they may adhere to the leaves
on which they are deposited: it may probably serve likewise for other
uses[616]. Another vessel is also to be found in the above butterfly, which
enters the oviduct above this, filled with a thick white fluid, the function of
which is, probably, to lubricate the passage[617]. A similar organ is found in
Phryganea grandis[618].

iv. Jelly-secretor (Corysterium). This is a remarkable organ, related to the
preceding, which secretes the jelly of Trichoptera, some Diptera, &c.; this
organ in the former, at least in Phryganea grandis, is of an irregular shape,
with four horns or processes[619].
Poison-secretor (Ioterium). This organ, which is most conspicuous in the
Hymenoptera Order, has not received much notice, except in the case of the
Hive-bee and the Scolia: in the former, it is an elliptical membranous
vesicle or reservoir, furnished at its lower extremity with a tube which
renders to the sting, and at the other by a blind, long, filiform, secretory,
vessel, which according to Swammerdam divides into two terminal blind
branches[620], though Reaumur could detect but one[621]; in this vessel the
poison is secreted and stored up. In Scolia there are two secretory vessels,
which enter the reservoir in the middle on each side[622]. In the Scorpion,
we learn from Marcel de Serres that the poison-secretor is clothed
externally with a horny thickish membrane, containing two yellowish
glands, composed of an infinity of spherical glandules, terminating in a
canal, enlarged towards its base so as to form a reservoir, and leading to the
extremity of the sting[623]. Connected by a slender tube with each mandible
in spiders is a vessel with spiral folds, which seems properly to belong to
this head—though Treviranus calls it a saliva-vessel[624]—since in the
Mygale avicularia and other spiders, the effect of the bite is said to be so
venomous as to occasion considerable inflammation, and sometimes
death[625].
v. Scent-secretors (Osmateria). Amongst other means with which insects
are gifted for the annoyance of their foes and pursuers, are the powerful
scents which many of them emit when alarmed and in danger. Concerning
the internal organs by which these effluvia are secreted we possess but little
information, but more notice has been taken of the external ones by which
they are emitted. We may conclude in general, that the secretory organs are
membranous sacs or vesicles, perhaps terminating in longer or shorter blind
filiform vessels, sometimes secreting a fetid fluid, and at others a fetid
gaseous effluvium. The Iulidæ, at least Iulus and Porcellio[626], cover
themselves when alarmed, with a fluid of this kind, or emit one, for this
faculty is not peculiar to the species noticed by Savi. I observed early in the
year, when I handled Iulus terrestris, that it was covered with a slimy

secretion, of a powerful scent, which stained my fingers of an orange
colour. The spiraculiform pores that mark the sides of the animal are the
outlets by which this fluid is emitted, and not spiracles as has been
supposed: each of these orifices, as we learn from Savi, terminates
internally in a black vesicle, which is the reservoir of the fluid[627]. The
most remarkable insect for its powers of annoyance in this way, is one on
that account called the bombardier (Brachinus crepitans), which can fire
numerous volleys of stinking vapour at its assailants before its ammunition
is exhausted[628]. M. Dufour has given a very particular account of the
organ that secretes this vapour;—it consists of a double apparatus, one on
each side, in the cavity of the abdomen, both formed of two distinct vessels.
The first, which is the innermost, presents itself under two different aspects,
according as it is contracted or dilated: in the former case it is a whitish,
irregularly rounded, soft body, apparently glandular, placed under the last
abdominal segments; communicating at one end with the reservoir, and
terminating constantly at the other in a very long and slender filament: in
the second case, or when it is dilated, it resembles an oblong, membranous,
diaphanous sac, filled with air, then occupying the whole length of the
abdomen, and appearing free except where it communicates with the
reservoir. The second vessel or reservoir is a small, spherical, brown or
reddish body, constant in its form, internally hollow, placed under the last
dorsal segment, precisely above the rectum, and opening by a small pore
into the anus[629]: so that the tail of this little beetle may be regarded as a
battery mounted with two pieces of cannon, which our alert bombardier
fires alternately without intermission till all his ammunition is expended.
The ground-beetles (Eutrechina) in general have a pair of these anal scent-
secretors, which discharge an acrid and caustic fluid, and sometimes a
volatile one[630]. The external organ of the scent-secretors in Gyrinus
consists of two minute hairy cylindrical retractile tubes, of a red colour[631].
Numerous insects of other tribes and genera emit scents from their anus,
and from various other parts of the body, of which having before given you
a very full account[632], I shall proceed to the consideration of the secretions
themselves: but first I must observe, that in many cases, as in some of the
cottony and powdery Aphides, Chermes, &c., the substance secreted
appears to be a transpiration through the pores of the body, a kind of
excretion from the superabundance of its fluid contents[633]. In many,

however, this secretion transpires through appropriate orifices: thus in
Chermes Abietis, which produces those curious galls resembling the cone of
a fir[634], the flocoons of seeming cotton that cover it proceed from little
oval concavities on its back, four of which are arranged in a transverse line
on each dorsal segment of the abdomen: these concavities have minute
tubercles probably terminating in a pore[635]. In Aphis Fagi the cottony
flocoons are almost an inch long[636].

The secretions of insects may be considered under the following heads—
Silk; Saliva; Varnish or Gum; Jelly; Oils; Milk; Honey; Wax; Poisons and
Acids; Odorous fluids and Vapours; and Luminous matter.
i. Silk. This valuable product of insects, while in the silk-secretor, assumes
in the Lepidoptera the appearance of a viscid gum, but the moment it is
exposed to the air it hardens into a silken thread. It is remarkable for the
following qualities:—it dries the instant it comes in contact with the air; it is
then insoluble not only in water but in the most active solvents, and even
heat has no effect upon it to melt or soften it: indeed, without these qualities
it would be of no use to us[637]. As soon as it leaves the spinneret it becomes
the thread we call silk, which being drawn through two orifices is
necessarily double through its whole length. This thread varies considerably
in colour and texture, as has been before stated[638], and sometimes
resembles cotton or wool rather than silk. In spiders it is of a much softer
and more tender texture than that of other spinning insects; and Mr. Murray
seems to have proved that it is imbued, in the case of the gossamer, with
negative electricity: in the sericterium the fluid that produces it is
sometimes white or grey, and at others yellow[639]. A remarkable gnat
(Ceroplatus tipuloides), living on an agaric, carpets its station of repose and
its paths with something between silk and varnish, which it spins, not in a
thread, but in a broad riband[640].
ii. Saliva. Many insects have the power of discharging from their mouth a
fluid which seems in some degree analogous to the saliva of larger animals.

Thus many, as Lepidoptera, Hemiptera, Diptera, &c., can dilute their food,
and render it fitter for deglutition. I have seen a common fly when not
employed in eating, emit a globule of fluid as big as a grain of mustard-seed
from its proboscis, and retract it again. On a former occasion I observed to
you that many predaceous, carnivorous, and some herbivorous beetles,
when alarmed emit a drop of coloured acrid fluid from the mouth[641]. That
this is not secreted in any of the ordinary salival vessels is evident from
Ramdohr's dissections of those beetles[642], who, had there been such an
organ, would doubtless have discovered it: but as the stomach of all of them
is distinguished by those minute cœca or blind vessels, which he
denominates shags (zotten)[643], perhaps these may be the secretors of this
fluid, probably analogous to the gastric juice[644]; in which case its primary
office would be the digestion of the food. We are not however warranted in
considering every fluid effused from the mouth as saliva. The glutinous
material with which wasps cement the woody fibres for their paper
edifices[645]; that with which some sand-wasps moisten the sand which they
scrape away, of which they form the singular tubes that lead to their
nests[646]; and that with which the aphidivorous larvæ fix themselves
previously to their becoming pupæ[647],—may be a secretion distinct from
saliva; possibly intermediate between it and gum or the matter of silk, and
secreted by peculiar organs. In the wasp, however, Ramdohr discovered
nothing of the kind[648]; and in Syrphus, as before observed, the saliva-
secretors are very peculiar in their structure, as if appropriated to the
secretion of a peculiar fluid[649]. Something similar has been observed by
Reaumur with regard to the larva of Crioceris merdigera, which forms its
cocoon with a kind of froth produced from the mouth[650].
iii. Varnish or Gum. The eggs of various insects, when they leave the
oviduct, are covered with a kind of varnish or gum by which they adhere to
the substances that the young larvæ are to feed upon, or are placed in a
proper position for their hatching in an appropriate station. Several
instances of this have been already mentioned[651]; I shall therefore not
enlarge further upon the subject. With regard to the secretion itself, little has
been recorded except its colour, which has been before noticed. Some
Lepidoptera also as we learn from Reaumur and Bonnet[652], use a varnish
in the construction of their cocoons.

iv. Jelly or Gluten. This secretion is particularly conspicuous in the
Trichoptera and some Diptera, serving as a bed or nidus for those eggs that
are committed to the water,—upon which I have nothing to add to what has
been before said[653]. Under this head also may be noticed the fluid,
secreted in peculiar vesicles, that lubricates the oviduct and the passages of
the sexual organs[654].
v. Oils. Oily substances are sometimes produced by insects. The common
oil-beetle (Meloe Proscarabæus) when touched sends forth a drop of this
kind of fluid, of an orange colour, from each joint of its legs[655]: something
similar I have observed in Coccinella bipunctata: Ray mentions a locust
taken in Spain which emits a yellow oleaginous fluid from between the
claws of its fore legs[656]; but the precise nature of these substances has not
been ascertained, nor whether they are secreted by peculiar organs.
vi. Milk. A milky fluid is produced by the larva of Chrysomela Populi.
Willughby observed a similar effusion from pores in the upper surface of
the body of Acilius sulcatus; and other insects emit it from other parts of
their body[657].
vii. Honey. It is certain that honey is not an animal secretion; yet the
saccharine matter collected from the nectaries of flowers, from which it is
derived, seems to undergo some alteration in the stomach; for the
consistence of honey is greater than that of any vegetable nectar, and its
taste does not vary greatly, while that of the nectar in different plants is
probably not the same. Reaumur also has observed, that each honey-cell in
a bee-hive is always covered by a cream-like layer of a thicker consistence
than the rest, which apparently serves to prevent the more liquid honey,
which from time to time is introduced under it, from running out[658]. Now
if honey were the unaltered nectar of plants, it is difficult to conceive how
this cream could be collected in proper proportions. The last-mentioned
naturalist likewise ascertained, that if bees, in a season in which the fields
afford a scarcity of food, be supplied with sugar, they will from this
substance fill their cells with honey which differs in no respect from the
common sort, except that its flavour is a little heightened[659]:—a similar
argument may be deduced from the circumstance of the bees imbibing the
juices of fruits of various kinds as they are well known to do[660]. It seems

therefore evident that the honey collected by bees undergoes some
modification in their honey-stomach before it is regurgitated into the cells,
and therefore may be regarded in some degree as a peculiar secretion.
Huber says that he has ascertained by a great number of observations that
electricity is singularly favourable to the secretion of the substance of which
honey is formed by flowers; the bees never collect it in greater abundance,
nor is the formation of wax ever more active, than when the wind is in the
south, the air humid and warm, and a storm gathering[661].
viii. Wax generally transpires through the pores of the skin of those insects
that produce it, either partially or generally, and it is secreted from honey or
other saccharine substances taken into the stomach. In the hive-bee, as has
been before stated, it is produced partially[662], but in many other insects it
is a general transudation of the body. This is particularly the case with a
large number of the Homopterous Hemiptera; and those flocoons that look
like cotton, and cover the body of several Chermes and Aphides, if closely
examined will be found of the nature of wax: this I have particularly noticed
with respect to Chermes Fagi, in which the cotton-like flocoons are often so
long as to cause the insect to look like a feather, and a leaf covered by them
exhibits a very singular appearance, as if clothed with the fine down of a
swan[663]. Probably the white powder or threads that appear to transpire
through the skin of many other insects is of a waxy nature. In the larva of a
beetle described by Reaumur, the flocoons are so arranged as to give the
animal some resemblance to a hedgehog, and when rubbed off they are
reproduced in twelve hours[664]. Gyllenhal, speaking of Peltis limbata,
observes, that when alive it is covered with a white powder resembling
mould, which if rubbed off returns again as long as the animal lives[665].
It will not be improper to include under this head what further account I
have to give of Lac, which though regarded as a resin, since Cocci
sometimes certainly produce wax[666], probably has some analogy with the
latter substance. When the females of this Coccus (C. Lacca) have fixed
themselves to a part of the branch of the trees on which they feed (Ficus
religiosa and indica, Butea frondosa, and Rhamnus Jujuba[667]), a pellucid
and glutinous substance begins to exude from the margins of the body, and
in the end covers the whole insect with a cell of this substance, which when

hardened by exposure to the air becomes lac. So numerous are these insects,
and so closely crowded together, that they often entirely cover a branch; and
the groups take different shapes, as squares, hexagons, &c., according to the
space left round the insect which first began to form its cell. Under these
cells the females deposit their eggs, which after a certain period are
hatched, and the young ones eat their way out. Though indisputably an
animal secretion, many of the properties of lac are not very different from
those of the juices of the trees on which the animal feeds, and which
therefore would seem to undergo but little alteration.
Wax seems also to form a constituent part of some insects which are not
found to secrete it. The yellow substance deposited in vessels containing
spiders in alcohol is said to be a true wax, and may be obtained from these
animals by gently heating them[668].
ix. Poisons and Acids. The bite as well as the sting of many insects is
followed by inflamed tumours, so that the sialisteria of some bugs, Diptera,
Aptera and spiders, may be regarded as producing a poisonous fluid; but we
know nothing of the real nature of it, nor of that of other venomous insects,
except the ant—whose celebrated acid may be considered under the present
head,—the bee, the wasp, and the scorpion.
Contrary to the once received doctrine that no acid was to be found in any
animal, except as the effect of disease in the alimentary canal, many insects
secrete peculiar and powerful ones. I have on a former occasion related an
instance in which an acid of this description, secreted in its sialisteria, is
employed by a moth to soften its cocoon[669]; and Lister mentions a species
of Iulus which produced one resembling that of ants[670]; but this last is the
most powerful of all. The fact that blue flowers when thrown into an ant-hill
become tinged with red has been long known; but Mr. Fisher of Sheffield,
about 1670, seems to have been the first who ascertained that this effect is
caused by an acid with which ants abound, and which may be obtained
from them by distillation or infusion in water[671]. Margraff and other
chemists confirmed this discovery[672]; and concluding that this acid was of
a peculiar kind, they gave it the name of the Formic acid. This name,
however, is now exploded; the subsequent experiments of Deyeux,
Fourcroy and Vauquelin having ascertained that the acid of ants is not of a

distinct kind, but a mixture of the Acetic and Malic[673]. These acids are in
such considerable quantities, and so concentrated in these animals, that,
when a number of Formica rufa are bruised in a mortar, the vapour is so
sharp that it is scarcely possible to endure it at a short distance. It also
transpires from them, for they leave traces of it on the bodies which they
traverse: and hence, according to the experiments of Mr. Coleridge, the
vulgar notion that ants cannot pass over a line of chalk is correct; the
effervescence produced by the contact of the acid and alkaline being so
considerable, as in some degree to burn their legs[674]. The circumstance of
much of the food of ants being of a saccharine nature may account for this
copious secretion of acid, the use of which is probably to defend themselves
and their habitations from the attack and intrusion of their enemies: if a frog
be put into a nest of Formica rufa that has been deranged, it will be
suffocated in five minutes[675]. That which they ejaculate from their anus
when attacked, as formerly stated[676], must be secreted in an ioterium; but
their very blood seems of an acid nature. It is very probable, as Dr.
Thomson has observed[677], that acids may be obtained from many other
insects, and that they are various modifications of the acetic.
From the circumstance that water is absorbed by greasy moths, that crystals
of a salt are occasionally found adhering to them, that they change blue
litmus paper red,—it has been inferred that their supposed oiliness is in fact
an acid or acid salt, having the property of attracting moisture from the air,
the infected moths being in fact not greasy, but wet; hence the application of
chalk and clay, usually recommended in this case, can have only a
temporary and superficial effect. The only effectual remedy, is steeping the
body in spirits of wine till all the acid is extracted[678]. This acid is probably
the same as Chaussier obtained from silkworms, since called Bombic
Acid[679].
The poison of bees and wasps, as to its chemical qualities, is a transparent
fluid, at first sweet to the taste, but immediately afterwards hot and acrid
like the milky juice of the spurge[680]; soluble in water, but not in alcohol;
and separable from the former in the state of white powder, when the latter
is added giving a slight red tinge to paper stained with vegetable blue, and
when dry and chewed appearing tenacious, gummy and elastic. This last
property, as well as solubility in water and not in alcohol, is common also to

the poison of the viper, which however differs in being tasteless, and not
affecting vegetable blues. From hence Fontana concludes that this fluid is
united with an acid, but in a very small proportion, and not with an
alkali[681]. The venom of bees is extremely active; a grain in weight, it is
conjectured, would kill a pigeon in a few seconds[682]. It is remarkable,
however, that while in some constitutions the sting of a single bee or wasp
is sufficient sometimes to induce alarming symptoms, in others numerous
punctures will produce little or no pain or inflammation. That this fluid, and
not the puncture of the sting, is the sole cause of the inflammation that
usually follows the wound inflicted by one of these animals, is proved by
the facts, that if it be introduced into one made by a needle, the same effect
ensues, and that when the whole contents of the poison-bag have been
exhausted by the insect's stinging three or four times in succession, its
weapon then becomes harmless[683].
The venom of scorpions, though much more potent, probably resembles
that of bees, &c., in many of its chemical qualities: it issues from two pores
in the sting before described[684], where, when the animal is irritated, it
accumulates under the form of two little drops of a whitish colour: spread
upon paper this fluid produces a spot like what would be caused by oil or
grease, and this part of the paper becomes by desiccation firmer and
transparent[685].

x. Odorous fluids and Vapours[686]. The powerful scents which different
insects emit are extremely numerous, much more so indeed than the
generality of Entomologists have been aware, for there is scarcely a scent
odious or agreeable that may not be met with in the insect world. This you
will be convinced of, by following a practice which I would recommend to
you—that of smelling the insects you take. Some of these scents are
peculiar to particular parts or organs, and some are exhaled generally by the
whole body; some are emitted by a fluid secretion, and others are gaseous
effluvia. On a former occasion I gave you a rather full account of these
scents and their organs[687]; I shall relate here only what I there omitted. To
begin with sweet odours. Many beetles emit an agreeable scent. The rose-
scented Capricorn or musk-beetle (Cerambyx moschatus) has long been
noted for the delicious scent of roses which it exhales; this is so powerful as
to fill a whole apartment, and the insect retains it long after its death.

Captain Hancock also informed me that another species of the same genus,
C. sericeus, has in a high degree a scent resembling that of the cedar[688] on
which they feed. Though most of the micropterous tribes (Brachyptera)
have a fetid smell, yet there are some exceptions to this amongst them. One
species (Philonthus suaveolens K. MS.) related to P. micans, which I once
took, smelt precisely like a fine high-scented ripe pear; another, Oxytelus
morsitans, like the water-lily; a third, O. rugosus, like water-cresses; and
lastly, a fourth (P. fuscipes) like saffron[689]: Trichius Eremita, one of the
Petalocerous beetles, is stated to have the scent of Russia leather; Geotrupes
vernalis, in spite of its stercorarious food, of lavender-water[690]. Mr.
Sheppard has observed that Dytiscus marginalis when recently taken smells
not unlike liquorice: Bonnet mentions a caterpillar that had the scent of new
hay. A little gall-fly (Cynips Quercus Ramuli) has the remarkable odour of
Fraxinella: the larva of another species of this genus (C. Rosæ) has an odour
which seemed to Reaumur as attractive to cats as that of Nepeta cataria or
Teucrium Marum[691]: some Phalangia smell like walnut leaves[692]; and
the various species of the genus Prosopis (Melitta * b. K.) have a very
agreeable scent of Dracocephalum moldavicum[692].
We next come to fetid odours. These in numerous cases are known to be
secreted and emitted by appropriate vessels and organs; they are often
exhaled from a fluid secretion, of which, in the letter lately referred to, I
gave you almost all the known instances. Savi, in his history of Iulus
fœtidissimus, informs us that it emits a yellow fetid fluid from its supposed
spiracles, which if applied in sufficient quantity imparts a red colour to the
skin, to be removed neither by friction nor washing, but only disappearing
by time; when removed from the black vesicles in which it is stored, it
shoots into very transparent octahedral crystals[693].
I have before mentioned the coloured fluid which some insects emit when
they are disclosed from the pupa, and that it probably exhales some
powerful odour which attracts the males[694].
The great Hydrophilus, in its larva state, when first taken into the hand
remains without motion; in a minute afterwards it renders itself so flaccid as
to appear like a cast skin. Taken by the tail it contracts itself considerably, it

then agitates itself briskly, and ejaculates with a slight noise a fetid and
blackish fluid[695].
In other cases these odours are produced by gaseous vapours. That of the
Bombardiers (Brachinus) is the most celebrated and remarkable. It is
whitish, of a powerful and stimulating odour, very like that exhaled by
nitrous acid. It is caustic, producing upon the skin the sensation of burning,
and forming instantly upon it red spots which soon turn brown, and which,
in spite of frequent lotions, remain several days. It turns blue paper red[696].
That amiable, intelligent, and unfortunate traveller Mr. Ritchie,—whose
premature death, when attempting to penetrate to the interior of Africa, all
lovers of Natural History so deeply lamented, and whose ardour in the
pursuit of that science I had an opportunity of witnessing, when, in
company with him, Messrs. Savigny, Du Fresne, and W. S. MacLeay in
1817, I visited the forest of Fontainebleau,—in a letter to the last-mentioned
gentleman[697], relates that his companion M. Dupont, near Tripoli took a
nest consisting of more than a thousand of a species of this genus. "I am
making a few experiments," says he, "on the substance which they emit
when they crepitate, but do not know whether I can collect enough to arrive
at any conclusion. It made Dupont's fingers entirely black when he took
them. It is neither alkaline nor acid, and it is soluble in water and in
alcohol." From this we may conjecture that it formed crystals.
xi. Phosphorus. On this remarkable secretion I have so fully enlarged on a
former occasion[698], that here I shall merely add a few observations which
Mr. Murray obligingly communicated to me. He remarks that in a box in
which glow-worms were kept—five luminous specks were found secreted
by the animal, which seemed to glow and were of a different tinge of light.
One put into olive oil at eleven p. m. continued to yield a steady and
uninterrupted light until five o'clock the following morning, and then
seemed, like the stars, to be only absorbed by superior effulgence. The
luminous spherical matter of the glow-worm is evidently enveloped in a sac
or capsule perfectly diaphanous, which when ruptured discloses it in a
liquid form, of the consistency of cream. M. Macaire, he observes, in the
Bibliothèque Universelle, draws the following conclusions from
experiments made on the luminous matter of this animal;—that a certain
degree of heat is necessary to their voluntary phosphorescence—that it is

excited by a degree of heat superior to the first, and inevitably destroyed by
a higher—that bodies which coagulate albumen take away the power—that
phosphorescence cannot take place but in a gas containing no oxygen—that
it is not excited by common electricity, but is so by the Voltaic pile—and
lastly, that the matter is chiefly composed of albumen.
xii. Fat. There is one product found in the body of insects most copiously in
their larva state, but more or less also in the imago, which may be called
their fat. In the former it is a many-lobed mass, occupying the whole of the
interior, except the space that is required for the muscles and the internal
organs, which it wraps round and protects. It is contained in floating
membranes, very numerous, which fill all the interstices, and assume the
appearance sometimes of small globules, and sometimes of a thickish
mucilage, which easily melts and inflames; in colour it is most commonly
white, but sometimes yellow or green. It is imagined to be a kind of
epiploon or caul, and is accumulated in the larva as a store of nutriment for
the growth and development of the organs of the perfect insect while in the
pupa state[699]. The blood in which the different organs float that is not
required for their nutriment, is supposed to be expended in the formation of
this substance. Marcel de Serres is of opinion that it is secreted from the
chyle by passing through the pores of the dorsal vessel, formerly called the
heart of insects[700].
Under this head I may mention what little is known with regard to the
perspiration of these animals[701]. That a considerable quantity of fluid
passes off from them when in the pupa state, is sufficiently proved by the
loss of weight which they undergo, and by the experiments of Reaumur,
who collected the fluid in closed glass tubes; and that in their perfect state
they are constantly passing off perspirable matter by the pores of their skin
or crust, is not only rendered probable by the succulent nature of their food
and the absence of any urinary discharge, but is proved by what takes place
in a swarm of bees. These insects, when crowded together in hot weather in
a large mass, become heated to such a degree, and perspire so copiously,
that those near the bottom are quite drenched with the moisture it produces,
which so relaxes their wings that they are unable to fly[702].
I am, &c.

LETTER XLII.
INTERNAL ANATOMY AND PHYSIOLOGY OF INSECTS,
CONTINUED.
REPRODUCTION.

The reproductive organs of insects in their general denominations and
functions correspond with those of the higher classes of animals; but as to
number, proportions, and other particular details of their structure, they
differ from them very considerably. I shall not now, however, enter at large
upon this subject, but confine myself principally to the consideration of
those organs in the female which are appropriated to the formation,
fecundation, maturation, exclusion and deposition of their eggs, and other
circumstances relating to that subject. The organs connected with this
function are the Sperm-reservoir; the Oviduct; the Ovaries; and the
Ovipositor.
I. The Sperm-reservoir (Spermatheca) is an organ connecting the vagina
with the oviduct, which, according to Herold, receives the male sperm as
into a reservoir[703], and fecundates the eggs in their transit through that
passage. This vessel, which consists of a double tunic, in the cabbage-
butterfly terminates the vagina, and is connected with the oviduct by a
lateral undulating tube: in shape it is a rather irregular oblong, and is
surmounted by a small orbicular vesicle, connected by a short tubular
footstalk with the main reservoir[704]. A similar organ was discovered by
Malpighi in the imago of the silkworm, who denominates it the uterus; to
which indeed it seems analogous, and which he also regards as a reservoir
for the sperm for the gradual fecundation of the eggs[705]. But in that fly the
organ is of a rather different shape, and the interior vessel terminates in
several spherical vesicles[706]. John Hunter by the most decisive
experiments, such as covering the eggs of the unimpregnated moth, after
exclusion, with the liquor taken from the spermatheca in those which had
been impregnated, and rendering them fertile, he demonstrated that this

organ was a reservoir for the spermatic fluid, to impregnate the eggs as they
were ready for exclusion, and that coition and impregnation were not
simultaneous[707]. It is not improbable that in all insects whose eggs are
gradually laid, this provision for their gradual fecundation, if carefully
sought for, might be detected[708]. Rifferschweils is of opinion, that in these
cases the eggs are fertilized in their transit through the oviduct by sperm
adhering to the folds of the cloacæ[709]: but this opinion seems less
analogous to what takes place in other cases, with regard to the due
preparation of the eggs for a safe and effectual transit[710].
II. The Oviduct (Oviductus) is the canal, always separate from the vagina,
which receives the eggs from the ovary, transmitting them, often by a
peculiar and complex instrument in which it terminates, to their proper
station. This canal sometimes opens into the anal passage or cloaca, and at
others, as in the cabbage-butterfly[711], is distinct, and lies between the
sexual organ and the anus. In the Arachnida there are two oviducts[712].
III. The Ovaries (Ovaria) in insects are the viscera in which the eggs are
generated and grow till they arrive at maturity, when they pass through the
oviduct, and are extruded or deposited in their appropriate station. They
vary considerably in their structure. In all however, except the Iulidæ, in
which there is only a single ovary[713], the oviduct at its upper or inner
extremity terminates in two branches, usually further subdivided into a
number of smaller conical ones, which several ramifications constitute the
ovaries, or egg-tubes as they are sometimes called: these tubes generally
consist of a single membrane, and are joined to the oviduct by membranous
rugose cloacæ[714]: in the Phalangia, however, there are two tunics; the
outer one of a cellular substance, and the inner one consisting of spiral
fibres like tracheæ—a kind of structure which renders them capable of
great extension[715]. Rifferschweils considers the ovaries as formed upon
two primary types.—First, flagelliform ovaries, consisting of conical tubes
equal in length, and inserted at the same place at the end of the primary
branches as in the Lepidoptera, the Bee, &c. Secondly, racemose ovaries,
consisting of short conical tubes, so proceeding from the primary branches
as to render the ovary racemose or pinnated, as in certain Neuroptera,
Coleoptera, and Diptera[716]: but perhaps their structure will be better
understood if they are divided into agglomerate ovaries and branching

ovaries: in the first the egg-tubes form two bundles, in which the branches
are not discernible, as in the Ephemera, the chamæleon-fly, and spiders[717]:
and in the second the branches are distinct, as in the Lepidoptera and the
majority of insects.
The number of branches varies in different genera and species. In
Echinomyia grossa, a large fly, there are only the two primary branches[718];
in the common dung-beetle (Geotrupes stercorarius) these appear divided
at their apex into fingers[719]: in Scolia, a Hymenopterous genus, and the
butterfly of the nettle, there are three secondary branches on each side[720]:
in many other Lepidoptera and the humble-bee there are four[721]; in the
common louse there are five[722]; in the rhinoceros-beetle and the
cockchafer, six[723]; in the wasp, seven[724]; eight in the cockroach[725];
twelve in the Carabi and the mealworm-beetle[726]; thirty in the large green
grasshopper (Acrida viridissima[727]); thirty-two in the cheese-maggot-
fly[728]; and in the hive-bee more than a hundred and fifty[729].
The number of eggs also contained in the ovaries varies. In Echinomyia
grossa there is only one egg in each, and only two at once in the matrix[730]:
in another fly produced by the cheese-maggot there are four[731]; in the
louse there are five; in the cockchafer six[732]; in the hive-bee sixteen or
seventeen are visible at the same time[733]; and in the silkworm-moth sixty
or seventy[734]. Besides the eggs, the tubes contain a pellucid mucus, and at
their upper extremity the eggs are lost in a granular mucous mass, in which,
however, they may still be discovered with a microscope[735]. With regard
to the termination of the ovaries or egg-tubes internally,—in those that have
agglomerated ones it is not to be traced, the whole appearing like an oblong
obtuse or acute body[736]: but in the branching ones it is more easily traced;
at first they converge in most cases to a point; this is seen to advantage in
the caterpillar of some butterflies, when near assuming the pupa, in which
they are readily discovered, and represent with great truth and elegance the
bud of some blossom[737]; but in time they diverge, and sometimes become
convoluted[738]; they generally terminate in a slender simple filament, but in
the louse in a fork[739]; they are sometimes extremely long, as in the wasp
and Lepidoptera[740]; in the hive-bee they appear to be shorter[741].

IV. We are next to consider the Ovipositor, or instrument by which
numerous insects are enabled to introduce their eggs into their appropriate
situations, and where the new-born larva may immediately meet with its
destined food. As this instrument is one of the most striking peculiarities
with which the wisdom of the Creator has gifted these little animals, and in
many cases is extremely curious and wonderful, both in its structure and
modes of operation—though on a former occasion I gave you a brief
account of several kinds of them[742], I shall now enter more at large into
the subject, and describe these often complex machines, as they are
exhibited in most of the different Orders of insects.
With regard to the Coleoptera Order, there are doubtless numerous
variations in the structure of this organ; but very few have been noticed, and
those chiefly belong to insects whose grubs feed on timber. In these it is
usually retractile one part within another, like the pieces of a telescope: in
Buprestis it consists of three long and sharp laminæ, the two lateral ones
forming a sheath to the intermediate one, which probably conveys the
eggs[743]: in Elater it is a cylindrical organ, terminating in a pair of conical
joints, which seem to form a forceps, and including a tube probably
conveying the egg to the forceps, which perhaps introduces it[744]. The
Ovipositor of Prionus coriarius differs from that of Callidium violaceum,
and many Capricorns before described[745]: it consists merely of a long
bivalve piece ending in a kind of forceps, and hollowed above into a
channel for the passage of the eggs[746].
In the Orthoptera the instrument of oviposition is more simple; in Locusta
consisting merely of four robust three-sided pieces, two above and two
below, the former pair at the end curving upwards and the latter
downwards[747], these pieces seem calculated when they have entered the
earth to enlarge the burrow, and the animal appears able to separate them
very widely from each other[748]. The ovipositor of Acrida viridissima,
which like that of many Hymenopterous insects forms a kind of appendage
or tail to the body, has been described both by De Geer and Latreille as
consisting of two valves only[749]; but in reality it consists of six, two upper
and four lower, as you may ascertain by means of a pin or the point of a
penknife, which will readily separate them. This is confirmed by a figure of
Stoll's of a species which seems to connect Conocephalus with Gryllus. In

this the ovipositor is considerably longer than the body of the animal, and is
composed of six distinct pieces; viz. two external ones stouter than the rest,
and within these four others finer than a hair and convolute at the apex[750].
There is a considerable variety in the shape of the ovipositors of the Acridæ
and the cognate genera:—thus in A. viridissima this organ is straight, in A.
verrucivora bent like a sabre, and in Pterophylla citrifolia and some others,
the whole machine is short and boat-shaped; in Scaphura Vigorsii it is also
rough with sharp little tubercles[751]. I had an opportunity of observing,
with respect to the first of these insects, that in boring, as is the case with
the Cicadæ and saw-flies, the motion of the valves was alternately
backwards and forwards. It appeared also to me that the two outer pieces of
each of the apparent valves were fixed in a groove in the margin of the
intermediate one. I saw this clearly with respect to the upper pieces, and it
is most probable that the lower are similarly circumstanced. In the cricket
tribe (Gryllus) the ovipositor is as long as the abdomen, very slender,
terminating in a knob[752]. It is apparently bivalve like that of Acrida, but I
believe is resolvable into the same number of pieces.
In the Homopterous Hemiptera there seems to be more than one type on
which the ovipositor is constructed. In an insect very common with us, the
froth froghopper (Cercopis spumaria), some approach is made to the
ovipositors last described, at least the number of pieces is the same—for it
has a pair of external valves forming a sheath, which includes three sharp
laminæ resembling the blades of a lancet, the middle one of which can be
separated into two; this instrument De Geer had reason to think was scored
transversely like a file[753]. In the insects of this Order so noted for their
song[754] (Cicada), there are only five pieces; namely, two valves forming
the sheath, two augers or borers, and an intermediate piece upon which they
slide, each being furnished with an internal groove for that purpose, and the
middle piece with a ridge to fit; a contrivance of Divine Wisdom, to prevent
their dislocation when employed in boring; the augers terminate in a knob
which is externally toothed[755]. This structure approaches that of the
Hymenoptera, especially the saw-flies. With regard to the Heteropterous
section of this Order—as they usually do not introduce their eggs into any
substance, they have no call for any remarkable ovipositor, and therefore
are not so furnished. A remark which will also apply to the Lepidoptera
Order.

In the Libellulina amongst the Neuroptera, an organ of this kind is
sometimes discoverable. In Agrion, Reaumur noticed a part which he
conjectured to be an ovipositor; it consists of four laminæ or lancets, the
interior pair slender, the exterior wider, and all externally serrated[756].
The insects of the Hymenoptera Order have long been celebrated for the
organs we are describing, whether used as saws, augers, or darts. I formerly
gave you a very general account of the saws,—I shall now give you a very
interesting one in detail copied from an admirable little essay of Professor
Peck. "This instrument," says he, "is a very curious object; and in order to
describe it it will be proper to compare it with the tenon-saw used by
cabinet-makers, which being made of a very thin plate of steel, is fitted with
a back to prevent its bending. The back is a piece of iron, in which a narrow
and deep groove is cut to receive the plate, which is fixed: the saw of the
Tenthredo is also furnished with a back, but the groove is in the plate, and
receives a prominent ridge of the back, which is not fixed, but permits the
saw to slide forward and backward as it is thrown out or retracted. The saw
of artificers is single, but that of the Tenthredo is double, and consists of
two distinct saws with their backs: the insect in using them, first throws out
one, and while it is returning pushes forward the other; and this alternate
motion is continued till the incision is effected, when the two saws receding
from each other, conduct the egg between them into its place. In the
artificial saw the teeth are alternately bent toward the sides, or out of the
right line, in order that the fissure or kerf may be made sufficiently wide for
the blade to move easily. To answer this purpose in some measure, in that of
the Tenthredo the teeth are a little twisted, so as to stand obliquely with
respect to the right line, and their point of course projects a little beyond the
plane of the blade, without being laterally bent; and all those in each blade
thus project a little outwards: but the kerf is more effectually made, and a
free range procured for the saws, by small teeth placed on the outer side of
each; so that while their vertical effect is that of a saw, their lateral effect is
that of a rasp. In the artificial saw the teeth all point outward (towards the
end) and are simple; but in the saw of the Tenthredo they point inward, or
toward the handle, and their outer edge is beset with smaller teeth which
point outwards (towards the end)[757]." Valisnieri, Reaumur, and De Geer
describe the groove as being in the back; but in Mr. Peck's insect, if there is
no error in his account, it is, as in the Cicadæ, in the saw itself[758]. In the

genus Cimbex, belonging to the same tribe, the saw differs in shape, being
somewhat sigmoidal or resembling the letter S, while in that of other saw-
flies it is cultriform with a concave edge: other minor differences
distinguish them, which need not be particularized.
A similar structure, with regard to the organ in question, obtains in the rest
of the Hymenoptera, even those that use it as a weapon of offence; but the
backs of the saws in them, composed of a single piece, become a sheath for
the darts. The valves, however, vary. In most of those with an exerted sting,
as Pimpla, they are linear, exerted, and as long as the aculeus itself[759]. In
Proctotrupes they appear to be united so as to form a tube for the
ovipositor, and are produced by a prolongation of the last abdominal
segment. The darts usually run in two grooves of the sheath, and at their
apex are retroserrulate[760]. In some cases the sheath itself is serrated[761].
The shanks of the darts are connected with the valves; so that when these
open they are pushed out: sometimes on their outer side they have a
triangular plate towards the base, which prevents their being pushed out too
far[762].
In Sirex and many ichneumons, in which the ovipositor is too long to be
withdrawn within the abdomen, it remains always exerted; but in general it
is retracted within that part when unemployed. In the gall-fly (Cynips) this
instrument is really as long as in Pimpla, &c.; but as it is infinitely more
slender, when in repose it is rolled up spirally and concealed within the
abdomen. It is the puncture of this minute organ that produces the curious
galls formerly described to you[763]. But the most anomalous ovipositor in
this Order appears to be that of Chrysis (C. ignita, &c.), which is covered
by several demi-tubes or scales enveloping and sliding over each other:
when these scales are removed, the true ovipositor appears, which is of a
structure similar to that of the rest of the Order, but the valves are long and
slender with their summit generally visible without the anus[764].
Though the ovipositor of the majority of Dipterous insects is a tube with
retractile joints[765], in the crane-flies this organ is different, and, like that of
Acrida above described, consists of what at first sight appear two valves,
but each of which is formed of two pieces, the upper ones sharp and longer,

and the lower pair blunt. The upper pair forms the auger that bores a hole in
the ground, and the lower conducts the eggs into it after it is bored[766].
In the Aptera and Arachnida in general there seems no remarkable
instrument of this kind; but Treviranus has described one in spiders for
extruding the eggs of a singular construction. It is an oval plate lying
between the external genitals and spinning organs, and is composed of a
number of small screw-shaped cartilages, connected together in the most
wonderful manner. There are few organs, he observes, in the animal
kingdom which for their artificial mechanism can be compared with this.
Each cartilage inosculates very closely in the adjoining one, and all are
besides bound together by a strong skin[767].
The manner in which the eggs of insects are fecundated by the male sperm
is one of those mysteries of Nature that are not yet fully elucidated and
understood. We can readily conceive that all the eggs may be fertilized by a
single intercourse in the case of insects which, like the Ephemeræ and
Trichoptera, exclude the whole mass at once; or like many moths and
butterflies, in a very short time afterwards; but the subject becomes much
more difficult to explain when we advert to the female of the hive-bee, the
whole number of whose eggs, deposited in two years, are, as Huber has
demonstrated, in like manner fertilized by a single act[768]:—if you bear in
mind, however, what I have lately observed with regard to Malpighi's
discovery of a sperm-reservoir in insects, you will more readily
comprehend how in this case a gradual fecundation may take place. The
principal objection to this solution of the difficulty in the case before us, is
derived from the very small size of the organ supposed to be destined for
this purpose—it being scarcely bigger than the head of a pin[769]: it seems
therefore incredible that it should retain any portion of an extraneous fluid
at the end of twelve or eighteen months, and still more unlikely that the
fluid should in the interval have sufficed for the slightest moistening of not
fewer than 30,000 or 40,000 eggs. The only hypothesis that seems at all to
square with this fact, is that of Dr. Haighton,—that impregnation is the
result not of any actual contact of the sperm with the eggs, but of some
unknown sympathetic influence[770], or rather perhaps of some penetrating
effluvia or aura seminalis, which, though small in quantity, it may retain the
power of emitting for a long period.

Certain female moths, of the species of that family which, from the
remarkable cases or sacs the larvæ inhabit, the Germans call sack—träger,
before noticed[771], have been supposed to have the faculty of producing
fertile eggs without any sexual intercourse; and various observers, after
taking great pains, appeared to have satisfactorily proved the fact; so that
some doubted whether these insects produced any males at all[772]. The
enigma was at length explained by the accurate Von Scheven. At first his
experiments were attended with the same result as those of his
predecessors; but upon making them more carefully, and separating what he
conceived to be the female from the male pupæ, he ascertained not only the
existence of a female in the species he examined (Psyche vestita), but that
when thus secluded she laid barren eggs; evidently proving that in the
contrary instances above alluded to, an unperceived sexual intercourse must
have taken place[773]. Though he thus ascertained that these insects do not
in this respect deviate from the general rule, he remarked or confirmed
several facts in their economy sufficiently anomalous and striking;—as that
the female is not only without wings, but with scarcely any feature of a
moth, much more closely resembling a caterpillar; and that in ordinary
circumstances she never attempts to leave the pupa-case in which she has
been disclosed, but that being there impregnated by the male, she there also,
apparently after the manner of the female Cocci, deposits her eggs, which
hatching produce young larvæ that make their way out of the case, and thus
seem to originate without maternal interference[774].
But the most remarkable fact bearing upon this head, though as relating to a
viviparous insect it does not strictly belong to it, is the impregnation of the
female Aphides, or plant-lice, before alluded to[775]. If you take a young
female Aphis at the moment of its birth, and rigorously seclude it from all
intercourse with its kind, only providing it with proper food, it will produce
a brood of young ones: and not only this; but if one of these be treated in
the same way, a similar result will ensue, and so on, at least to the fifth
generation!! to which period Bonnet, who first made an accurate series of
observations on this almost miraculous fact, successfully carried his
experiments, till the approach of winter and the want of proper food forced
him to desist[776]; and Lyonet extended it still further[777]. It is now
generally admitted as an incontestible fact, that female Aphides have the
faculty of giving birth to young ones without having had any intercourse

with the other sex. How are we to explain this most extraordinary fact? Are
we to suppose with Bonnet that these insects are truly androgynous, as
strictly uniting both sexes in one? This supposition, however, is completely
overturned by the circumstance, that there are actually male as well as
female Aphides, and that these, as was first observed by Lyonet, are united
towards the close of the summer in the usual manner[778]. The most likely
supposition therefore is, that one conjunction of the sexes suffices for the
impregnation of all the females that in a succession of generations spring
from that union. It is true that at the first view this supposition appears
incredible, contradicting the general laws and course of nature in the
production of animals. But the case of the hive-bee, stated above, in which
a single intercourse with the male fertilizes all the eggs that are laid for the
space of two years, and in the case of a common spider mentioned by
Audebert[779], for many years, shows that the sperm preserves its vivifying
powers unimpaired for a long period, indeed a longer period than is
requisite for the impregnation of all the broods that a female Aphis can
produce; and if immediate contact with the fluid be not necessary, who can
say that this is impossible? It is, however, one of those mysteries of the
Creator that human intellect cannot fully penetrate. But this anomaly in
nature is not wholly confined to the Aphides; since Jurine has ascertained
that the same thing takes place with Daphnia pennata Müll (Monoculus
Pulex L.), one of Branchiopod Crustacea[780]. It is worth observing whether
the female Aphides in their natural state, I mean those of the summer or
viviparous broods, have intercourse with the male. I think I have noticed
males amongst them; but they seem to become most numerous in the
autumn, preparatory to the impregnation of the oviparous females. The
object of this law of the Creator is probably the more ready multiplication
of the species[781].

As to the period of gestation, most insects begin to lay their eggs soon after
fecundation has taken place: but in some Arachnida, as the Scorpion, which
seems to be both oviparous and ovo-viviparous, nearly a year intervenes,

and the eggs increase to four times the size which they had attained at that
period, before they are extruded[782]. The time that is required to lay the
whole they are to produce, varies also in insects. In this respect they may be
divided into two great classes:—those namely which deposit the whole at
once, as Ephemerina, Trichoptera, &c., and those which deposit them in
succession, occupying in this operation a longer or shorter period. Many in
the first class, as the Trichoptera or caseworm-flies, envelope their eggs in a
gelatinous substance[783], which renders their extrusion in a mass more
easy. Of the second class, which includes by far the greater proportion of
insects, some exclude the whole number in a very short period, others
require two or three days or a week, as the cockroach[784]; and others, as the
queen-bee, not less than two years. The eggs in the ovaries of the last vary
infinitely in size; those that have entered the oviduct have arrived at
maturity, while the rest grow gradually smaller as they approach the
capillary extremity of the tubes, where they become at length invisible to
the highest magnifier[785]. In many insects the eggs seem nearly to have
reached their full growth previously to the exclusion of the female from the
pupa; and this exclusion and the impregnation and laying of the eggs
rapidly succeed each other. One moth (Hypogymna dispar), which is
remarkable for the number of eggs she contains, sometimes deposits them,
even before they are fecundated, in the pupa-case[786]. But in other cases the
sexual union is not so immediate, and some time, longer or shorter, is
requisite for the due expansion of the eggs; and the ovaries of the animal
swell so much, as often to enlarge the abdomen to an extraordinary bulk:
this is seen in a very common beetle (Chrysomela Polygoni) that feeds upon
the knot-grass; but in no insect is it so striking as in the female of the white
ants, whose wonderful increase of size after impregnation I have related to
you on a former occasion[787].

I shall conclude this subject with a few observations upon ovo-viviparous
insects; supposed neuters, and hybrids, which, though they do not fall in

regularly under any of the foregoing heads, may very well have a place in
this letter.
1. It has already been observed that there are a few ovo-viviparous
insects[788], the young of which exist in the ovaries at first as eggs, but are
hatched within the body of the mother, and come forth in the living form of
a larva and sometimes even of a pupa. Of the first description are certain
Diptera, the Aphides, and the Scorpion.
Reaumur has described two modes in which the larvæ of the first are
arranged in the matrix of the mother. In some they are heaped together
without much appearance of order, being placed merely parallel to each
other[789]; but in others they are arranged in a kind of riband—the length of
the little animals, which are also parallel, forming its thickness—rolled up
like the mainspring of a watch[790]. These larvæ in general are not divided
into two masses corresponding with the pair of ovaries in other insects, but
form only a single one[791]. You must not suppose that these little fetuses lie
naked in the womb of the mother; each has its own envelope formed of the
finest membrane, which, however, is not entirely divided from that of those
adjoining to it, but appears to be one tube, which becomes extremely
slender between each individual, so as when drawn out to look like a
chain[792]. Reaumur seems to have thought that in these flies the larvæ were
never confined in any other case or egg[793]; but De Geer sometimes found
eggs in the body of Sarcophaga carnaria, though most generally larvæ,
from which he conjectures that it is really ovo-viviparous, the eggs being
hatched in the body of the mother[794]. As these flies are all carnivorous,
and their office is to remove putrescent flesh, you may see at one glance the
object of Providence in this law of nature—that no time may be lost, and
the animal exercise its function as soon as it is disclosed from the matrix.
The Aphides, so fruitful in singular anomalies, are ovo-viviparous, as I have
before hinted[795], at one period of the year, that is during the summer, but
strictly oviparous at its close. From the experiments of De Geer, however,
upon Aphis Rosæ, it would appear that this faculty is not conferred upon the
same individuals, but only upon those of different generations of the same
species; all the generations being ovo-viviparous except the last, which is
oviparous[796]: nor does it appear, as has been sometimes imagined, that it is

common to the whole genus. De Geer observed a species in the fir, which
makes curious galls resembling a fir cone (Aphis Abietis), which appeared
never to be ovo-viviparous[797].
With regard to scorpions, it does not seem clear that they are always ovo-
viviparous: M. Dufour twice found in the midst of the eggs nearly mature, a
young scorpion which appeared to him at large in the cavity of the
abdomen; it was so large that it was difficult to comprehend how it could
possibly be excluded from the animal, without an extraordinary
operation[798]. The pupiparous insects (Hippobosca, &c.) have been
sufficiently noticed before[799].
2. I have already in several of my former letters stated to you what the
modern doctrine of physiologists is with respect to certain individuals,
usually forming the most numerous part of the community with insects
living in society, that were formerly supposed to be neuters, or as to their
sex neither male nor female—that they are in almost every instance a kind
of abortive females, fed with a different and less stimulating food than that
appropriated to those whose ovaries are to be developed, and in
consequence in most instances incapable of conception[800]. Upon these
sterile females, you also heard, devolve in general the principal labours of
their respective colonies, showing the beneficent design of Providence in
exempting them from sexual cares and desires, and meriting for them the
more appropriate name, now generally used, of workers. The differences in
the structure of the female bee and the workers were also then accounted
for; and similar reasoning may be had recourse to with regard to those of
ants, in which the worker and the female differ still more materially. My
reason for introducing this subject here, is to observe to you that I have
some grounds for thinking that this system extends further than is usually
supposed, and that to each species in some Coleopterous and other genera
there are certain individuals intermediate between the male and female; this
I seem to have observed more especially in Copris and Onthophagus. For in
almost every British species in my cabinet of these genera I possess such an
individual, distinguished particularly by having a horn on the head longer
than that of the female, but much shorter than that of the male. I once
observed a pair of Pentatoma oleracea, a very pretty bug, in coitu, both
sexes being ornamented with white spots, and by them stood a third

distinguished from them by red ones. I do not, however, build on this
circumstance, though singular; but mention it merely that you may keep it
in your eye. It would be curious should it turn up, that, to answer some
particular end of Providence, in some tribes of insects there are two kinds
of males, as in the gregarious ones two descriptions of females.
I am, &c.

LETTER XLIII.
INTERNAL ANATOMY AND PHYSIOLOGY OF INSECTS,
CONCLUDED.
MOTION.

We have seen upon a former occasion the great variety of movements that
insects can perform, and of the external organs with which they perform
them[801]: but we are now to consider the internal apparatus, by the
immediate action of which they take place—their system of muscles. When
we reflect upon the wonderful velocity, their size considered, with which
many insects move, and the unparalleled degree of muscular force that
many exert[802], we feel no small degree of curiosity to know something of
that part of their internal structure that produces these almost incredible
effects. I shall in the present letter endeavour in some degree to gratify that
curiosity, and give you an account of the muscles of these little animals,—
first considering them in general; and then, as far as my information goes,
adverting to those in particular that move the different parts and organs of
an insect's body.
I. The muscles of insects may be considered in general as to their Origin;
Substance and Parts; Shape; Colour; Kinds; Attachment; and Motions.
i. Origin. The origin of the muscular fibre in the higher animals is from the
blood, the globules of which, by their coagulation in a series, appear to
form it[803]; and in insects it is derived from the same universal source of
nutrition and accretion, but not till it has been concreted into the adipose
tissue or epiploon before noticed[804]. In the pupa of the cabbage-butterfly,
Herold observed that this substance first assumed a fine flocky appearance
and a blue-green colour, and that from it so changed were produced tender
bundles of muscular fibres, extending in various directions, the epiploon
itself decreasing in proportion as they were formed[805].

ii. Substance and Parts. The muscular fibre in vertebrate animals appears to
consist of globules arranged in a series, and of no larger diameter than those
of the blood,—the mean diameter of which in the human subject, when
measured under the microscope by a micrometer, is found to be about 1⁄5000th
part of an inch[806]. When Cuvier published his immortal work in 1805, the
powers of any magnifier then constructed were not sufficient to enable this
great physiologist to arrive at the simple fibre[807]; but Mr. Bauer, by the use
of improved glasses, amongst other discoveries that will immortalize his
name, was the first to detect, under the directions of Sir E. Home, the
ultimate thread of which the muscular bundles are composed[808]. Chemists
distinguish the substance of which we are speaking, by the name of fibrine.
By the abundance of azote or nitrogen that enters into its composition, it
possesses a character of animalization more marked than any other animal
substance; and its elements are so approximated in the blood, that the
slightest stagnation causes them to coagulate: and the muscles are without
doubt, in the living subject, the only organs that can separate this matter
from the mass of blood, and appropriate it to themselves[809]. The primary
bundles of muscles are formed of the simple fibres, and the secondary are
the result of an aggregation of the primary. The smaller bundles are not
always exactly parallel to each other, but must in many cases diverge more
or less, to produce those variations in shape observable in the muscles
themselves: there are intervals therefore between the bundles, which in
some animals are filled by a cellular substance[810]. Probably much of this
statement will apply in most instances to the muscles of insects, but we may
conclude that the globules that form them are infinitely smaller[811]. Lyonet
has given some interesting observations with regard to those of the
caterpillar of the Cossus: he describes them as of a soft transparent
substance, capable of great extension, covered and filled by silver tubes of
the bronchiæ, penetrated by the nerves, and containing oily particles. Each
muscle was enveloped in membrane, and was composed of many parallel
bands, consisting of bundles of fibres enveloped likewise in separate
membranes. The fibres themselves, (but it is doubtful whether he arrived at
the ultimate term of muscular fibre,) in a favourable light and under a good
magnifier, appeared to be twisted spirally[812]. In spiders the muscles
seemed to him to consist of two substances, the one soft and the other hard,
the last forming a kind of stiff twisted filament[813]. A muscle thus

composed of different bundles of fibres may be stated as to its parts, in
insects, to consist of base, middle, and apex: the base is that part by which
they are fixed to any given point of the internal surface of the crust, or of
one of its processes, which serves as their fulcrum; the apex is that part by
which they are fixed, either mediately or immediately, to the organ to be
moved; and the middle is the remainder of the muscle. We usually discover
in them no inflation of the middle corresponding with the belly of the
muscles in vertebrate animals; they occasionally, however, terminate in a
tendon, as those of the thighs and legs; but these tendons are of a different
nature from the fibrous ones of warm-blooded animals; for they are hard,
elastic, and without apparent fibres: the fleshy ones of the muscle envelope
them, and are inserted in their surface[814].
iii. Shape. The muscles of insects are usually linear, with parallel sides;
some are cylindrical, as those of the wings of the Libellulina[815]; and
others, as those that move the legs in the caterpillar of the Cossus, are
triangular[816]. In the suctorious mandibles of the grub of a common water-
beetle[817] they are penniform, or shaped like a feather; and some in the
Cossus are forked[818]. Under this head I may also observe, that the muscles
are sometimes extremely slender threads, crossing each other, and often
curiously interwoven in various directions, so as to resemble lace or fine
gauze, as may be seen in the alimentary canal of some caterpillars[819];
sometimes also they surround part of this organ, like a series of minute
rings[820].
iv. Colour. The most usual colour of the muscles of insects is white: those
for flight however, according to Chabrier, differ from the rest, by being of a
deeper and reddish colour[821]; and I have observed likewise that those in
the head of the stag-beetle, when dried at least, are red, and look something
like the flesh of warm-blooded animals.
v. Kinds and Denomination. In general, muscles may be regarded as divided
into primary and secondary—the primary being the muscles by which the
principal movements of any organs are effected, and the secondary their
auxiliaries which are the cause of subordinate movements[822]. Every
muscle almost has its antagonist, the action of which is in an opposite
direction; so that when it is equal, the organ to which they are attached

remains without motion; but when that of one preponderates, a movement
in proportion takes place[823]. The principal antagonist muscles that may be
found in insects are the following. 1. Levator muscles that raise an organ,
and Depressors that depress it. 2. Flexors that bend an organ, and Extensors
that unbend or extend it. 3. Abductors that draw an organ back, and
Adductors that draw it forwards. 4. Constrictors that contract an opening,
and Laxators that relax it. 5. Supinators that turn the underside of an organ
upwards, and Pronators that return it to its natural situation. Some of these
muscles in insects, like some of their articulations and their spinal
chord[824], seem to exercise a double function,—thus the levators and
depressors of the wings are constrictors and laxators of the trunk[825]. At
first it may seem that insects, not having the power of turning up the hand,
cannot have the Supinator and Pronator muscles; but some muscle of this
kind must be in the Gryllotalpa, and in those that have a versatile head[826].
v. Attachment and Insertion. The attachment and insertion of the muscles in
insects in general is to the interior of the crust, or to some of its internal
processes as a fulcrum, and to the organ to be moved. In some cases,
however, the muscles act upon the organ by the intervention of other
bodies. Thus, those that move the wings are often attached to little bones, as
Chabrier calls them[827], which are connected with the base of the wings by
ligaments. In the Dynastidæ and other Lamellicorns, and the Libellulina,
&c., a remarkable provision is made for giving a vast increment of force to
the muscles of the wings, by means of caps or cupules surmounted by a
tendon, which receive their extremity; the tendon terminating in a fine point
attached to the wing, and thus more muscles are brought to bear upon it[828].
Chabrier seems to think that, in some cases, the back that intervenes
between each pair of wings is the medium by which the muscles act upon
it[829].
vi. Motions. Irritability is the universal distinction of the muscular fibre,—
when put in action by the will or involuntarily, it causes it to contract or
become shorter; and the intermediate agents of the will and other causes are
the nerves, which, as galvanic experiments seem in some degree to prove,
are the conductors of an invisible fluid or power which immediately causes
that action. If a nerve is divided, the muscles to which it renders obey it no
longer, evidently proving that the nerves cause muscular irritability[830].

How this contraction is immediately effected,—whether the fibre, as some
suppose, undergoes any crispation, or becomes zigzag[831], or whether there
is any sudden change in their chemical composition that rapidly and
strongly augments their cohesion, as Cuvier hints[832], cannot be clearly
ascertained, unless a Bauer could submit the living fibre to his glasses. All
that we know certainly on the subject is, that muscles alternately contract
and relax at the bidding of the will or involuntarily, and so occasion all the
movements of animal bodies.
II. Having considered the muscles of insects in general, I must next make a
few observations, as far as my means of information will enable me, upon
those that move their different parts and organs—at least the principal ones;
since to descend to minutiæ would be an endless and unprofitable labour.
As larvæ, except those whose metamorphosis is semicomplete[833], differ
widely in their system of muscles from perfect insects, I shall begin my
observations with them.
We owe by far the most accurate and detailed account of the muscles of
larvæ to the illustrious Lyonet, who, with incredible labour and patience
without example, dissected the caterpillar of the Cossus, and has described
every air-vessel, every nerve, and every muscle that could be detected by
the microscope. Cuvier also has given a description of the muscles not only
of caterpillars, but of the larvæ of the Lamellicorn beetles, the Hydrophili,
and the Capricorn beetles[834]. From these sources are derived what I have
now to lay before you. If you look at one of Lyonet's plates[835], the layers
of longitudinal muscles look like so many parallel ribands, others run in an
oblique, and others again in a transverse direction[836]. He divides them into
dorsal, ventral, and lateral muscles[837], terms which sufficiently explain
themselves. Of the longitudinal muscles there are four principal rows[838],
the others are more numerous. The principal object of these muscles, which
are flexors and extensors, is to shorten or lengthen the body, or to act on any
particular segment as the circumstances of the animal may require. I shall
not here notice the muscles of the head and legs, as they are not remarkably
different from those of perfect insects. The prolegs are moved by two
muscles—the anterior one covering in part the posterior—of a remarkable
structure: one of their points of attachment is by many branches or tails to
the sole of the foot, and by several heads to the skin of the animal; so that

they can draw the proleg within the body or push it out, and perform other
necessary movements[839].
I shall now call your attention to the muscles of the perfect insect, as they
move the head and its organs; the Trunk; the Abdomen; and the Viscera.
i. The Head. This part in insects moves upwards, downwards, inwards, to
right and left, is pushed forth or drawn in, is often capable in part of a
rotatory movement, and is sometimes versatile, turning as it were upon a
pivot. All these movements are of course produced by an appropriate
apparatus of muscles, which have their attachment in the anterior part of the
trunk, mostly in the manitrunk, while their insertion is in the posterior part
of the head, in the margin of the occipital cavity. To enumerate and describe
them all would be tedious and uninteresting—I shall only mention some of
the principal ones. The levators of the head are usually a pair of muscles
situated in the manitrunk, to the upper side of which they are attached, and
perhaps in Coleoptera and some others to the phragma, which probably
Cuvier means by the anterior part of the scutellum[840]; they are inserted in
the posterior margin of the upper part of the head, in Coleoptera in a pair of
notches (Myoglyphides[841]), or a single one[842]. In Cordylia Palmarum
these muscles as they approach the head, to judge from the dead animal,
divide into two branches or a fork: thus, as the muscle-notches are wide in
this insect, the muscle acts upon each extremity of the sinus—these
branches appear to be tendinous[843]. The depressors of the head are the
antagonist muscles to the above, and have their attachment to the
antepectus and its antefurca[844]. A circumstance distinguishes these
muscles in many Coleoptera, that seems hitherto to have been overlooked.
If you take the common dung-beetle (Geotrupes stercorarius), and carefully
extract the head with its muscles from the trunk, you will see on each side
of the depressors a subovate corneous scale, of a pitch colour[845], which is
attached only to the muscle, and designed to strengthen it: if you then
examine the anterior cavity of the manitrunk, you will perceive on each
side, just within the lower margin, a minute triangular scale, of a similar
substance; these ligaments, like the pax-wax, or ligamenta nuchæ, in
mammalia, though in a lower situation, are doubtless intended to sustain the
action of the muscles.

With regard to the moveable organs of the head—the antennæ, maxillæ,
palpi, tongue, mandibulæ, &c., have each their appropriate apparatus of
muscles: but I shall only notice those of the last, the mandibulæ. These are
principally abductors and adductors to open and shut them: from the work
that the jaws of some insects have to do, you may conjecture that they must
be furnished with powerful muscles. In caterpillars and other larvæ, in
which state the action of the mandibles is most in requisition, the muscles
are what Cuvier calls penniform[846], and are attached on each side to a
tendinous lamina or cartilage. In the grub of Dytiscus the power and
magnitude of the adductor muscle is wonderful[847]. In the Orthoptera this
structure of the mandibular muscles takes place also in the imago[848]; but
in the Coleoptera, at least in the stag-beetle and some others that I have
examined, these muscles in this state have no cartilage or tendon. Their
attachment is always to the parietes of the head, of the cavity of which the
adductors, in some cases, occupy a considerable portion[849]. As to their
insertion—these last, in some Orthoptera, enter more or less the interior of
the mandible[850]; but commonly they are inserted at or near the interior
angle of the mandibular basal cavity, and the abductors at the exterior.
ii. The Trunk. We have little information with regard to the muscles of the
parts of the trunk itself, by which, in some insects, the manitrunk is enabled
to move independently of the alitrunk: it is more probable that the levators
have in part at least their attachment to the anterior surface of the
prophragm[851], than that the levators of the head should be there fixed, as
Cuvier seems to think; since both the phragma and the ligament that
appears in many cases to close the cavity of the manitrunk round the
viscera[852], would prevent all communication between those muscles and
any part connected with the scutellum: probably the depressors have their
attachment partly on the anterior face of the medifurca[853]. These points,
however, must be left to future investigators.
With regard to the organs of the trunk, we have more certain and
satisfactory information;—the muscles of the legs having been described by
Lyonet and Cuvier, and those of the wings most particularly by Chabrier. In
caterpillars, the muscles are situated in the interior of the articulations that
form the legs: they consist of several bundles appropriated to each, which
have their attachment in the parietes of the preceding joint, near the margin,

and are inserted in the margin of that they move[854]. Lyonet counted
twenty-one muscles in the leg of the caterpillar of the Cossus; but eight of
these were appropriated to the claw, or rather formed a pair of
semipenniform muscles, having their insertion at the inner angle of its
base[855]. In perfect insects, according to Cuvier, each joint of the legs is
furnished with a pair of antagonist muscles—a flexor and extensor, the
former being the lower, and the latter the upper muscle; and this pair has its
insertion in the joint it moves, and its attachment usually in the preceding
one: but those of the coxæ—which are rotators, causing it to turn
backwards or forwards—and the extensor of the thigh, have their
attachment in the parietes of the trunk, and to the endosternum; one of the
rotators of the anterior coxa, and the extensor of the anterior thigh to the
antefurca; of the intermediate pairs to the medifurca, and of the posterior to
the postfurca[856]. Every joint of the tarsus has also its flexor and extensor.
In the ground- and water-beetles (Eutrechina and Eunechina), &c., whose
posterior coxæ are immoveable, the thigh includes two pair of antagonist
muscles[857]. In extracting the posterior leg of Necrophorus Vespillo I
observed more than a single pair of muscles that had their attachment in the
coxa; and probably many other variations in this respect exist.
Little was known with respect to the most interesting part of the muscular
apparatus of insects, that by which such wonderfully rapid and varied
motions are imparted to their organs of flight, till Chabrier undertook to
elucidate it; which he has done in a manner that will confer a lasting honour
upon his name, as one of the most able successors to Swammerdam and
Lyonet in their peculiar department. He has given a most admirable account
of the internal anatomy of the trunk of insects in general, as far as it relates
to their flight; particularly of that of the cockchafer (Melolontha vulgaris),
of one of the Libellulina (Æshna grandis), and of a bumble-bee (Bombus);
and I believe he has thus illustrated insects of some of the other Orders, but
his memoirs on these I have not had an opportunity of consulting. What I
have to say on this subject, therefore, will be principally derived from what
he has communicated with respect to the above insects.
A considerable difference in the volume of the muscles of the wings takes
place in insects according to the force of their flight. Where it is rapid and
powerful, the alitrunk is nearly filled by them, and the alimentary canal is

much attenuated; but in those whose flight is feeble, they occupy less space,
and the alimentary canal is proportionally enlarged[858]. In the Lepidoptera,
Hymenoptera and Diptera, the principal muscles of both wings have their
attachment in the anterior portion of the alitrunk[859]; in the Coleoptera, in
the posterior[860]; and in the Libellulina, those of the anterior wings are
confined to the anterior portion, and those of the posterior pair to the
posterior[861]. The muscles for flight in general differ from others by their
mass, length, and colour; the bundles of fibres are very distinct, strong, and
parallel; their direction is uniform, according to the motion they are to
produce; their fibres are either attached to the solid parts to be moved, or to
cupules, but they never terminate in a tendon; the muscles are perfectly
independent of each other, and the wings can be moved by them
separately[862]. As to their denomination and kind—the principal ones are
the levators and depressors, which with respect to the trunk, as was before
observed, are constrictors and laxators. The levator muscles form several
distinct bundles in Coleoptera, Lepidoptera, &c.; in the Diptera there are
three[863]; in the Libellulina they seem to be single, are all environed with a
blackish pellicle, with numerous aërial vesicles, symmetrically arranged,
filling the interstices[864]. The most common number is a levator to each
wing; there are often, however, as in the cockchafer and the dragon-fly, two
depressors[865]: but in the Hemiptera, Lepidoptera, and saw-flies (Serrifera)
amongst the Hymenoptera, the secondary wings have distinct levators, but
not depressors[866]; the other insects of that Order have only a pair of
each[867]. The other wing-muscles are of a secondary description, and
auxiliary to the above. Their office is to extend and close the wings: so that
though the denomination of extensor will suit the former, that of flexor is
not so proper for their antagonists; their office being not so much to bend,
as to bring back the wing to its station of repose. The folding of certain
wings, as those of Coleoptera, Dermaptera, the Vespidæ, &c., seems more
the function of the abdomen than of the wing-muscles; this you may easily
see, as I have often done, if you attend to any Staphylinus, when after
alighting from flight it proceeds to fold up its wings under the elytra.
Perhaps the term retractor might not be inapplicable to the muscles in
question. Both these and the extensors are usually small slender muscles,
but sometimes numerous[868]. They are larger in the Coleoptera,
Lepidoptera, and saw-flies[869]. The muscles that open and shut the elytra of

Coleoptera, and probably of Heteropterous Hemiptera, and which also aid
their movements during flight, are very slender[870]. With regard to the
attachment and insertion of the wing-muscles, it is according to two very
distinct types, one of which appertains to insects in general, and the other is
peculiar to the Libellulina. In insects in general, the principal muscles for
flight have not their insertion in the wings, but act upon their bases by the
intervention of small long pieces. The depressors occupy the middle and
upper region of the alitrunk, and are inserted anteriorly and posteriorly upon
the concave surfaces of two transverse horny semi-partitions, adapted by
their elasticity to dilate the trunk—and thus acting the part of both
diaphragm and ribs[871]: but in the Libellulina, as in birds, these muscles are
placed on each side of the point of support of the humerus[872]; the
depressors being attached immediately to the wings without it, and the
levators within it, with this sole difference, that they are connected to the
internal extremity of the base of the wing by the intervention of a cupule
terminating in a tendon; all are disposed perpendicularly to the arms of the
levers on which they act, and all incline more or less outwards, the one to
dilate, and the other to contract the trunk[873]. It may be observed in
general, that in insects formed upon the first type, the great action of these
muscles is the dilatation and contraction of the alitrunk, the main tendency
of which is to depress and raise the wings[874]. I shall add here a few words
upon the attachment of the wing-muscles in the different Orders: but first I
must request you to read what I have said on the partitions and chambers of
the alitrunk in a former letter[875]. In most insects of the first type, the
depressors are longitudinal dorsal muscles that have their posterior point of
attachment in the metaphragm (costale Chabr.); but the anterior varies:—in
those that have elytra, tegmina, or hemelytra, the muscles for them seem to
be contained in the chamber, varying in size, that lies between the
prophragm and mesophragm; and the anterior point of attachment of their
depressor muscles is the mesophragm: they are also attached in some to the
metathorax or back of the posterior portion of the alitrunk[876]. The levator
muscles in Coleoptera, at least in the cockchafer, by a long tendon have
their posterior attachment in the lower part of the posterior coxæ[877], their
anterior attachment to the solid parts to be moved. In the Cockchafer and
the Dynastidæ, but not in Geotrupes, on each side of the cavity of the
metathorax under the base of the wing is a large and small cupule, which

from their lateral situation one would think must receive the levator
muscles—apparently unnoticed by M. Chabrier; but as there is a pair of
these cupules on each side, there must have been also a pair of muscles
attached to them, which does not agree with his statement[878]. In the
Hymenoptera and Diptera the anterior attachment of the depressors is to the
back of the alitrunk and to the prophragm, and the levators to the breast,
and the sides of the back of the trunk[879]. In the Libellulina the depressors
and levators that terminate, by a tendon surmounting a cupule, in the base
of the wings, have their posterior attachment in the breast. These cylindrical
muscles with their cupule and tendon look like so many syringes[880].
Having thus described to you the powerful muscular apparatus by which,
either mediately or immediately, the wings of insects are moved, it will not
be out of place if I add a few words upon their flight itself. The great object
in this is to generate a centrifugal force which may counteract the weight of
the body. Its wings are the external organs by which the insect as it were
takes hold of the air when they fall, and is impelled by it when they rise; its
head makes way for it; its abdomen, as a rudder, steers it; and by alternately
increasing and diminishing in volume, and rising and falling, enables it to
win an easy way through the fluctuations of the atmospheric sea. The trunk
by its elasticity admits the internal action of antagonist muscles, which by
turns compress and dilate it; an action promoting the elevation and
depression of the wings, and keeping up the elasticity of the internal air,
which is thus now rarified and now condensed: in the former state flowing
like a tide, accompanied by the blood, into the nervures of the wings[881],
and thus increasing their tension and centrifugal force;—in the latter ebbing
and receding to the trunk, thus relaxing the one and diminishing the other.
The spiracles by which the air enters or is expelled, open and shut at the
animal's pleasure[882]; and besides, many insects are furnished, as we have
seen[883], with numerous vesicles or reservoirs, which can give out a supply
of internal air when wanted: and thus they can vary their aërial motions,
diminish or increase the counteracting centrifugal force; rise and fall, and
move onwards and in different directions, as their occasions demand.
iii. The Abdomen is perhaps capable of the greatest variety of motions of the
three primary sections of the body. Even when the insect is reposing, a
constant dilatation and contraction usually takes place in it[884]; and from its

annular structure, its parts capable of separate motion are numerous:—it
expands and contracts; it rises and falls; it bends in various directions; and
its segments can often be lengthened or retracted. Besides all this, its
spiracles open and shut, and its reproductive and other anal organs have
their appropriate motions. In numerous Coleoptera, however, and some
Hemiptera, the upper-side of the abdomen is almost the only part that is
moveable, especially near the trunk; the under-side, having its first
segments soldered together, is only capable of motion near the tail[885]. The
muscles that produce the various motions of this part must be entitled to all
the denominations stated above[886]. I have on a former occasion explained
to you how, in insects that have a petiolate abdomen, that part is elevated
and depressed[887]. In those with a sessile one the base is attached to the
metaphragm by strong ligaments[888], and the muscles that move the first
piece act from one segment to another. The partial movements of the
segments of this part, where they have place, are produced by muscular
fibres which extend from the whole anterior margin of one to the whole
posterior one of that which precedes it. If those, for example, of the back
contract, the abdomen becoming shorter above, bends upwards; and if those
of the sides or belly, it bends sideways or downwards[889]: this is a beautiful
as well as simple contrivance.
The alternate rush of air from the abdomen into the alitrunk, and from the
atmosphere into the abdomen, is attended by the constriction or expansion
of that part as it rises or falls in flight[890], which seems to require the action
of constrictor and laxator muscles.
iv. The Viscera. Having before had occasion sufficiently to notice the
muscles by which the systole and diastole of the dorsal vessel of insects is
maintained[891], I shall now only mention those that are woven round their
alimentary canal, by which the peristaltic motion of that organ, causing its
contractions and the propulsion of its contents, takes place. One would at
first think that a view of the intestines of any animal could under no
circumstances afford any very pleasing spectacle to the eye of any but a
scientific spectator; but any lady who is fond of going to Disons to be
tempted with an exhibition of fine lace, would experience an unexpected
gratification could she be brought to examine those of a caterpillar under a
microscope: with wonder and delight she would survey the innumerable

muscular threads that in various directions envelope the gullet, stomach,
and lower intestines of one of these little animals; some running
longitudinally, others transversely, others crossing each other obliquely, so
as to form a pattern of rhomboids or squares; others again, surrounding the
intestine like so many rings, and almost all exhibiting the appearance of
being woven, and resembling fine lace,—one pattern ornamenting one
organ; another, a second; and another, a third. This will suffice to give some
idea of this part of the muscular structure of these little animals[892].
Lyonet counted the muscles contained in the body of the caterpillar of the
Cossus. In the head he found 228; in the body, 1647; and enveloping the
intestines, no less than 2186; which, after deducting 20 that are common to
the gullet and the head, gives a total of 4061[893]. In the human subject only
529 have been counted[894]: so that this minute animal has 3532 muscles
more than the Lord of the creation!

The muscles of the Arachnida seem less numerous than those of insects. In
the Scorpionidea they appear to be robust, formed of simple straight fibres,
of a whitish gray colour: a muscular web, rather strong, clothes the parietes,
but rarely adheres to them, of the abdomen, and envelopes the viscera, with
the exception of the lungs, and probably of the heart. The dorsal part of this
web gives birth to seven pairs of filiform muscles, which traverse the liver,
and are attached to a muscular riband which, passing above the lungs, runs
the whole length of the ventral parietes. These muscles when exposed to
view resemble extended cords. The abdominal segment preceding the tail is
filled with a powerful muscular mass which moves that organ[895].
Treviranus discovered two longitudinal muscles in Scorpio europæus,
running from the breast to the tail, which above and below each gill were
connected by another running transversely across the heart, thus forming a
quadrangular area in which the gills are situate[896]. The heart appears to be
moved by muscles not very dissimilar to those of the Cossus[897], as is
likewise that of the Araneidea; in Clubiona atrox the wider part of this

organ is muscular, and incloses a considerable cavity[898]. In this tribe the
muscles of the abdomen, the skin of which is soft and unfit to act as a lever
to them, are attached to a cartilage, and thus their action is better
sustained[899].
Having thus laid before you all of importance that I can collect with regard
to the apparatus of muscles discoverable in insects, I shall next say
something upon a few other points connected with that subject. When I
enlarged upon their motions, I related a few instances of the extraordinary
power of that apparatus[900] in leaping ones; but this power is not confined
to that circumstance. The flea, not more remarkable for its compressed
form, enabling it to glide between the hairs of animals, and its elastic coat
of mail, by which it can resist the ordinary pressure of the fingers, than for
its muscular strength, has attracted notice on this account from ancient
times. Mouffet relates that an ingenious English mechanic, named Mark,
made a golden chain of the length of a finger, with a lock and key, which
was dragged by a flea;—he had heard of another that was harnessed to a
golden chariot, which it drew with the greatest ease[901]. Another English
workman made an ivory coach with six horses, a coachman on the seat with
a dog between his legs, a postillion, four persons in the coach, and four
lacqueys behind—which also was dragged by a single flea. At such a
spectacle one would hardly know which most to admire, the strength and
agility of the insect, or the patience of the workman. Latreille mentions a
flea of a moderate size dragging a silver cannon on wheels, that was
twenty-four times its own weight, which being charged with powder, was
fired without the flea appearing alarmed[902]. Many caterpillars are
accustomed to extend their bodies from a twig, supported merely by the
four hind feet, in one fixed attitude, either in an oblique, horizontal, or
vertical direction, either upwards or downwards, and that for hours together.
We may conceive what prodigious muscular force must be exerted upon
this occasion, by reflecting that the most expert rope-dancer, though endued
with the power of grasping with his feet like a bird with its claws, could not
maintain himself in a horizontal position even for an instant. Bradley asserts
that he has seen a stag-beetle carry a wand half a yard long and half an inch
thick, and fly with it several yards[903]. Some insects have the faculty of
resisting pressure in a wonderful degree. If you take a common dung-chafer
(Geotrupes) in your hand and press it with all your strength, you will find

with what wonderful force it resists you; and that you can scarcely
overcome the counteraction, and retain the insect in your hand: was it not
for this quality, the grub of the gad-fly must be crushed probably in passing
through the anal sphincter of the horse[904]. But that of Eristalis tenax
affords a more surprising instance of this power of counteraction:—an
inhabitant of muddy pools, it has occasionally been taken up with the water
used in paper-making, and strange to say, according to Linné, has resisted
without injury the immense pressure given to the surrounding pulp[905]; like
leather-coat Jack mentioned by Mr. Bell[906], who, from a similar force of
muscle, could suffer carriages to drive over him without receiving any
injury. Almost as remarkable is the state of extreme relaxation into which
the muscles of some larvæ fall, when their animation is suspended; and the
revived tension to which a subsequent resumption of the vital powers
restores them. Bonnet having suspended the animation of the caterpillar of
Sphinx Ligustri by keeping it submerged, squeezed it between his fingers,
until it had wholly lost its cylindrical form and was as flat and supple as the
empty finger of a glove; yet in less than an hour the very same caterpillar
became as firm, as compact, as cylindrical, and in short, as well, as though
it had never been submitted to treatment so rough[907].

It is fortunate that animals of a large size, as has been well remarked,
especially noxious ones, have not been endowed with a muscular power
proportionable to that of insects. A cockchafer, respect being had to their
size, would be six times stronger than a horse; and if the elephant, as Linné
has observed, was strong in proportion to the stag-beetle, it would be able
to pull up rocks by the root, and to level mountains[908]. Were the lion and
the tiger as strong and as swift for their magnitude as the Cicindela and the
Carabus, nothing could have escaped them by precaution, or withstood
them by strength. Could the viper and the rattlesnake move with a rapidity
and force equivalent to that of the Iulus and Scolopendra, who could have
avoided their venemous bite? But the Creator in these little creatures has
manifested his Almighty power, in showing what he could have done had he
so willed; and his goodness in not creating the higher animals endued with
powers and velocity upon the same scale with that of insects, which would
probably have caused the early desolation of the world that he has made.
From this instance we may conjecture, that after the resurrection, our bodies
by a change in the structure and composition of their muscular fibre—for
we know that their locomotive powers and organs, as far as the muscle is
concerned, will then be of a very different nature[909]—may become fitted
for motions and a potent agency of which we have now no conception.
This wonderful strength of insects is doubtless the result of something
peculiar in the structure and arrangement of their muscles, and principally
their extraordinary power of contraction, excited by the extent of their
respiration: for animals that respire but little, as the fœtus in the womb and
the pullet in the egg, have very little contractile muscular power[910]. To get
some idea from facts of this extraordinary contractile power in insects,—
extract the sting of a bee or a wasp, with its muscles, which appear to be
attached to powerful cartilaginous plates[911], and you will find it continue
for a long time to dart forth its spicula, almost as powerfully as when
moved by the will of the animal. A still more extraordinary instance of
irritability is exhibited by the antlia, or instrument of suction of the
butterfly. If this organ, which the insect can roll up spirally like a
watchspring or extend in a straight direction, be cut off as soon as the
animal is disclosed from the chrysalis, it will continue to roll up and unroll
itself as if still attached to its head: and if after having apparently ceased to

move for three or four hours it be merely touched, it will again begin to
move and resume the same action. This surprising irritability and
contractility of muscle doubtless depends upon the peculiar structure of the
antlia, which is composed of an infinite number of horny rings, acted upon
by muscles, more numerous probably than those which move the trunk of
the elephant. The motion only ceases when the muscles become dry and
rigid.

I have already, under another head[912], considered the annual sleep, or
winter state of torpidity of insects, during which an intermission for the
most part of muscular motion and action takes place. I shall now make a
few observations with respect to their diurnal sleep, which may very
properly have its place in the present letter. That insects, usually so
incessantly busy and moving in every direction, require their intervals of
repose, seems to call for no proof. We see some that appear only in the day,
and others only in the night, others again only at certain hours; which leads
to the conclusion, that when they withdraw from action and observation, it
is to devote themselves to rest and sleep. The cockchafer flies only in the
evening; but if you chance to meet with it roosting in a tree in the earlier
part of the day, you will find it perfectly still and motionless, with its
antennæ folded and applied to the breast:—we cannot indeed say that its
eyes are shut; for as insects have no eyelids, that sign of sleep can never be
found in them. Again, if a Lepidopterist goes into the wood to capture
moths in the day-time, he finds them often perched on the lichens that cover
the north side of the trunk of a tree, with their wings and antennæ folded,
and themselves without motion, and insensible of his approach and their
own danger. Thus it was that I captured that rare insect the lobster-moth
(Stauropus Fagi) in the New Forest. Some, however, have asserted that the
caterpillar of the silkworm, except when they moult, never intermits feeding
day or night, and consequently does not sleep: but the accuracy of this
statement, both from analogy and observation, admits of great doubt.
Malpighi informs us that these caterpillars for an hour and more, twice a
day, remain immoveable with their heads bent down as though asleep, and

even if disturbed, resume again the same inactive posture[913]; and other
larvæ in great numbers certainly seem to have regular intermissions from
eating of considerable duration: those called Geometers, for hours together
remain motionless projected from a twig, to which they adhere by their
posterior prolegs alone; and the processionary caterpillars make only
nightly sorties from their nests, passing the day in inaction and repose[914].
Bees have been often seen by Huber, when apparently wearied with
exertion, even in the middle of the day, to insert the half of their bodies into
an empty cell, and remain there, as if taking a nap, without motion for half
an hour or longer[915]; and at night they regularly muster in a state of sleep-
like silence. Mr. Brightwell once observed an individual living specimen of
Haltica concinna, which appeared to remain motionless on the same spot of
a wall for three successive days.
Before concluding these remarks on the Internal Anatomy and Physiology
of Insects, I shall explain to you, as you will probably feel inclined
occasionally to pursue the subject, the best mode of dissecting them.—By
far the most useful dissecting instruments for this purpose are very fine-
pointed and sharp scissors, as these will enable you to divide the
integument and separate other parts with much less risk of injuring their
delicate structure than any knife. These scissors are what Swammerdam
chiefly used; and he had some so extremely small and fine, that he was
necessitated to employ a lens when he sharpened them. If to these be added
a sharp and fine-pointed knife or two, some needles fixed in handles, also
fine-pointed—(you will find them more convenient than any other
instrument for detaching minute parts and fibres,) a pair of fine and
accurately adjusted pliers, and an assortment of camel's-hair brushes,—you
will be nearly set up as an Entomological dissector. You will still, however,
require a small dissecting table, with a projecting and moveable arm for
lenses of various descriptions, so as to admit both the hands to be employed
upon the subject under examination; and for this purpose probably no
contrivance can be better adapted than that of Lyonet, of which the figure in
Adams On the Microscope will convey a better idea than any
description[916].
Previously to dissecting any insect, it must be killed by plunging it into
boiling water, which is recommended by Lyonet, or spirits of wine or of

turpentine; and it is often useful to let larvæ remain a few days in the latter,
by which means the vessels become firmer and stronger. The parts of pupæ
become much more distinct if they are boiled for a few minutes: and the
same mode may be adopted in the examination of spiders.
The most convenient mode of proceeding, which was that also of Lyonet, is
to dissect the insect in water, or, to avoid putridity, in diluted spirits,—if
small, upon a concave glass, to which it should be fastened by means of a
little melted wax; if larger, in the bottom of a common chip box, surrounded
with a border of wax to retain the fluid. The integuments of the insect, being
carefully divided longitudinally with scissors, should if flexible be turned
back, and fixed by small pins stuck in by a fine pair of pliers, while the skin
at the same time is stretched by another. After making such observations as
present themselves without further dissection, the viscera must be
cautiously extracted, washing away the fat which surrounds them with
spirits of turpentine, in which it is soluble, applied by camel's-hair pencils.
After separation they may conveniently be examined by putting them into
water, and gently shaking them so as to cause the parts to unfold. If
endowed with the patience of Swammerdam, you may even arrive at
injecting these minute parts with wax or coloured fluids, conveyed by
delicate glass tubes having one end as fine as a hair, which he also
employed to fill the viscera with air; and afterwards drying them in the
shade, and anointing them with oil of spike in which a little resin had been
dissolved, he succeeded in preserving them. If it is not convenient to finish
the dissection of an insect at once, it should be covered with spirits of wine.
Swammerdam found a mixture of spirits and distilled vinegar very useful
for keeping caterpillars previously to dissecting them, as it consolidated the
parts[917].

And now having brought to a close my long wanderings in this ample and
intricate field, and having threaded, as well as my slender powers and
limited knowledge enabled me, the infinite turnings and convolutions of
this Dædalean labyrinth—the Anatomy and Physiology of insects,—will

you not own that the volume of wonders I have laid before you proves
irrefragably that, though these minims of nature apparently rank so low in
the scale of being, yet in their structure, instead of being, as might be
expected, more simple, they are infinitely more complex and highly
wrought than those animals that are placed the nearest to ourselves? the
Creator in the latter doing every thing by a beautiful simplicity; while in
the former, the more to magnify his power and skill, because they afford no
apparent space for it, by a wonderfully curious and intricate multiplicity:
and whether we study the one or the other, we shall in both trace the
footsteps of that adorable Love which has shown attention to the comfort
and well-being of the lowest insect, as well as of the highest of his
creatures.
I am, &c.

LETTER XLIV.
DISEASES OF INSECTS.

Having laid before you what observations I thought might sufficiently
explain all the principal features of the Anatomy of insects both external
and internal, you will next expect to be informed whether, like the higher
animals, they are subject to have the admirable order observable in their
frame interrupted by Disease; and you will perhaps imagine, from the
multiplicity of their organs and vessels, that they must be peculiarly
exposed to derangements of the vital and other functions. That they have
their diseases is certain; but, except in the case of their appropriate parasitic
assailants, which is a part of their economy, it does not appear that their
maladies are more numerous and frequent than those of other animals. The
same Almighty Power which endowed them with so complex a structure,
generally upholds them in health during their destined career, until they
have fulfilled the purpose of their creation, when they die and return again
to their dust[918].
But perhaps I may seem to you as making too great a parade about these
little insignificant creatures if I assign a separate letter to the consideration
of their diseases: but when you recollect that Aristotle has a chapter on this
subject[919], and that the learned Willdenow has devoted a distinct portion
of his excellent introductory work on Botany to the diseases of Plants[920],
—you will perhaps be of a different mind: indeed, some facts I shall have to
communicate are so remarkable and interesting, that I am sure, when you
have read this letter, you will not think the subject one that deserves to be
slighted.
Insect diseases may, I think, be divided into two great classes; those
resulting, namely, from some accidental external injury or internal
derangement, and those produced by parasitic assailants.
I. Under the first head we may begin with wounds, fractures, mutilations,
and other extraneous causes of disease. To these—insects are peculiarly

subject; and though they are not, like the Crustacea and Arachnida[921] and
some other invertebrate animals, endowed with the power of reproducing a
mutilated limb, yet their wounds appear to heal very rapidly, and at the time
they are inflicted to produce little pain[922]. But if those important members,
their antennæ, are mutilated, insects seem to suffer a kind of derangement;
the great organ of their communication with each other, and in various
respects with the external world, being removed, all their instincts at once
fail them. I formerly related how the amputation of these affects the queen-
bee[923]. A similar result, as Huber tells us[924], follows, when the same
experiment is repeated on the workers or drones: they immediately become
unable to take any further part in the labours of the hive; they can no longer
guide themselves except in the light; if they petition one of their fellow-
citizens for honey, they are unable to direct their tongue to its mouth to
receive it; they remain near the entrance of the hive, and when the light is
intercepted they rush out of it to return no more.
Insects occasionally are subject to tumours or a preternatural enlargement of
their parts and organs. The antennæ of bees sometimes swell at their
extremity so as to resemble the bud of a flower ready to open, becoming at
the same time very yellow, as does the fore part of the head[925]. I once saw
a specimen of a Hydrobius—agreeing with H. fuscipes in every other
respect even to the most minute punctum—which had a large tumour on
each side of the prothorax, evidently accidental, occasioned probably by the
stoppage of the pores by which the superfluous moisture and air escape
when it undergoes its last change. The converse of this I have observed to
take place sometimes in the same part of Geotrupes foveatus, the ordinary
lateral foveæ becoming very considerably enlarged;—this was the case with
the specimen from which Mr. Marsham made his description of that insect.
The species is, however, very distinct in other respects, and may always be
known by its small size. It happens now and then also, that these tumours
represent blisters. I saw one once on one elytrum of a beetle and not on the
other. Those of Serropalpus (as Mr. MacLeay, on the authority of M.
Clairville, informs me) are particularly subject to this disease. But, of all the
organs, the wings are most exposed to derangements of this kind. De Geer,
in a specimen of Pieris Cratægi just excluded from the chrysalis, observed
that one of these was distended by a considerable quantity of extravasated
green fluid—two or three large drops following an incision. This disease

appeared to arise from the lower membrane not adhering to the upper; so
that the nervures—which are rather longitudinal channels, being open
below, than tubes—were not closed to confine the fluid to its proper course.
The malady, which might be called a dropsy of the wing, carried off the
insect the day after its exclusion[926]. Reaumur observed that the wings of
some flies were affected by an air-dropsy, as he calls it, which appeared to
arise from the air escaping from its natural channels, and thus separating,
the two membranes that form the wing, and filling the cavity produced by
their separation[927].
Sometimes also monstrosities are to be met with in these animals, or
variations from a symmetrical structure in organs that are pairs. I have a
beetle in which the terminal joint of one of the maxillary palpi is short,
ovate, and acute; and that of the other, long, semiovate, and rather obtuse. A
specimen of Blaps mortisaga in my cabinet, taken by Mr. Denny, besides
the terminal mucro of the elytra, has a long diverging lateral one. Goeze
had the larva of a Semblis brought to him in which one of the two fore-legs,
though perfect in all its parts, was only half the length of the other[928];
which he regarded as a reproduction, but it seems rather a malformation.
Müller mentions a most extraordinary fact of one of the Noctuidæ, which
when disclosed from the pupa retained the head of the larva[929]. One of the
most remarkable instances of this kind that have fallen under my own
observation, may be seen in a specimen of Chrysomela hæmoptera in the
cabinet of our friend Curtis; in which one of the thighs produces a double
tibia, but only one of these is furnished with a tarsus.
The diseases of insects which arise from some internal cause are not very
numerous. The first that I shall mention is a kind of vertigo. "Ants have also
their maladies," says M. P. Huber: "I have noticed one extremely singular;
the individuals attacked by it lose their power of guiding themselves in a
straight line, they can walk only by turning round in a circle of small
diameter and always in the same direction. A virgin female shut up in one of
my glasses was seized on a sudden with this distemper; she described a
circle of an inch in diameter, and made about a thousand turns in an hour, or
not quite seventeen in a minute. She continued constantly turning round for
seven days, and when I visited her in the night I found her still in motion. I
gave her honey—and I think that she ate some of it." He observed that some

workers were attacked by a similar disease: one of these, however, had the
power of walking from time to time in a straight line; when placed upon its
head it continued its gyrations[930]. Similar motions of a little moth,
mentioned on a former occasion[931], may perhaps have been produced by
the same cause. Bees are also subject to vertigo, which has been attributed
to their eating poisonous honey[932]—but may not this disease in all these
cases arise from some derangement of the nervous system? One of the ants
which was so affected had lost one of its antennæ; but as this was not the
case with the others, no great stress is to be laid upon the circumstance.
Huber does not inform us whether those attacked by this disease recovered
or not.
I have observed more than once, that the flesh-fly and some others of the
same tribe are subject in particular seasons to a kind of convulsions. When
thus attacked, they kick and struggle, and seem unable to fly. Sometimes
they lie upon their backs without motion, but if a finger be placed near them
their convulsive motions are renewed. When thrown into the air, instead of
flying, they fall to the ground. Had this distemper occurred earlier or later in
the year I should have attributed it to the benumbing effects of cold; but as
my observations were made one year (1816) in May, and in another (1811)
in the latter end of June, this could scarcely be the case. In the year last
mentioned I observed that many flies died under its influence. In wet
seasons this tribe is subject to another disease, which proves fatal to many
of them, and indeed to other Diptera. A white crust appears to be formed
upon the abdomen both above and below, of a granular appearance, much
resembling fine moist sugar. On the back of that part this crust does not
cover the margins of the segments, which gives it the appearance of white
bands; so that deceived by it, I have often at first flattered myself that I had
met with some new species. The under-side of the abdomen is wholly
covered by it, divided in the middle into two longitudinal masses, the anal
segment being bare. De Geer has noticed this or a similar disease, which,
when flies are attacked by it, causes the abdomen to swell so as even to
burst, and the segments become dislocated. Upon opening the abdomen it is
found filled with a white unctuous substance, which often accumulates (as
above described) on its external surface[933]. Dr. Host says that in this
disease when the animal is dead, the wings, which were before incumbent,
become extended, and its almost invisible pubescence grows into long

hairs[934]. De Geer seems to think that these flies are thus affected in
consequence of having eaten some poisonous food[935]; but I rather suspect,
as I have observed it become prevalent chiefly in wet seasons, that it arises
from a superabundance of the nutritive fluid, or of the fat, so that it seems to
be a kind of plethora. I once observed a fly fixed to a pane of glass, round
which was a semicircle of what appeared to be merely vapour, whose radius
was nearly three-fourths of an inch. Taking it for an aqueous fluid that had
transpired from the dead animal, I paid no further attention to it at that time:
but observing from day to day that the moisture did not evaporate, after two
or three months had elapsed, I had the curiosity to examine it more closely,
and, upon scraping some of it off with a penknife, I found it was a white
substance of a fatty nature. In this case, then, the fat must have exploded on
all sides with considerable violence from half the body or the abdomen.
Probably this was a more intense degree of plethora. When I examined this
appearance the fly had fallen off, and I could not find it.
Mr. Sheppard once brought me a panicle of grass, the glumes of which were
rough with hairs, or small bristles, to which several specimens of a fly
related to Xylota pipiens adhered by their proboscis. At first I thought that
having been entrapped by the bristles, and unable to extricate themselves,
they had perished from want of food; but since when touched they readily
dropped from the glumes, some other cause, perhaps disease, probably
occasioned this singular suspension of themselves.
The maladies to which bees and silkworms are subject are more interesting
to us than those of flies, on account of their utility as cultivated insects. One
of the worst distempers which attacks the first of these animals is a kind of
looseness or dysentery: this happens early in the year, when they are fed
with too much honey without any portion of bee-bread[936], and sometimes
destroys whole hives. Their excrements, instead of a yellowish red, then
become black, and the odour they emit is insupportable; the bees no longer
observe their usual neatness, inducing them to leave the hive when they
void their excrements, but they defile it, their cells, and each other. Several
remedies have been prescribed for this disease. To prevent it, a syrup made
by an equal mixture of good wine and honey is recommended; and as a
cure, to place in the hive combs containing cells filled with bee-bread[937].
But one of the worst maladies to which these useful animals are subject, is

that called by Schirach Faux Couvain. It originates with the larvæ; and is
caused either by their being fed with unwholesome food, or when the
queen, as sometimes happens, lays her eggs so that the head of the grub is
not in a proper position for emerging from the cell when the period for its
disclosure is arrived:—the consequence is, that in both cases it dies and
becomes putrid, which sometimes produces a real pestilence in a hive. The
remedy for this evil is to cut away the infected combs, and to make the bees
undergo a fast of two days[938]. The hive should be cleaned and fumigated,
by burning under it aromatic plants.
The cultivators of the silkworm in France have given names to several
diseases to which that animal is subject. One is called La Rouge, and is
supposed to be occasioned either by too great heat, or by too sudden a
transition from cold to heat. It takes place when the caterpillar is first
hatched; which lives perhaps, but in a very sickly state, till it should spin its
cocoon and assume the pupa, when it expires. Another degree of the same
disease is called Les Harpions or Passis. A second distemper of this animal
is Des Vaches, Le Gras or La Saune: this is a mortal disease, supposed to be
of a putrid nature, and produced by mephitic air; it shows itself after the
second moult, but rarely after the subsequent ones. When a caterpillar is
first attacked, changing the air may prove a remedy; but when the disease
has made progress, it is best to burn or bury them, since if the poultry pick
them up they might be poisoned by them. A third disease of silkworms is
called Les Morts Blancs, or Tripes, which is also occasioned by impure air,
when the leaves the animal feeds upon are heaped so as to produce
fermentation. The caterpillars attacked by it die suddenly, and preserve after
their death the semblance of life and health. Too great heat, whether
artificial or natural, occasions La Touffe, a fourth, which, when the heat
continues long, destroys all those that are arrived at their last stage of
existence in their larva state. Black points scattered over different parts of
the body, or livid and blackish spots in the vicinity of the spiracles,
followed by a yellowish or reddish tint, are symptoms of a fifth malady,
called La Muscardine. After this the animal soon dies, and becomes
mouldy, but does not stink. This disease is not contagious, and is thought to
be caused by a moist heat, attended by pernicious exhalations. La Luzette,
Luisette, or Clairène, is another malady, which shows itself most commonly
after the fourth moult. It seems to arise from some original defect in the

egg. The caterpillars attacked by it may be known by their clear red and
afterwards dirty white colour; their body becomes transparent, and the
matter of silk exudes in drops from their spinnerets; consequently, though
as voracious as the rest, they are never able to construct a cocoon, and
should be destroyed. Les Dragées is the name given to cocoons which
include a larva that never becomes a pupa. The cause of this disorder has
not been ascertained, and whole broods are sometimes subject to it, which,
as in the last, seems to imply some defect in the eggs. But as the caterpillar
spins its cocoon, and the silk is as good as usual, it is a malady of no great
importance. Lastly, sometimes the mulberry leaves have a gummy rather
acrid secretion, which purges the silkworms; their excrement is no longer
solid; they become weak and languid; and if the secretion is abundant, their
transpiration is impeded, and at the time of moulting they are become so
feeble as to be unable to cast their skin[939].
In the case of many caterpillars of Lepidoptera that died, Bonnet found by
dissection that the disease was remotely occasioned by a diarrhea, which
taking place immediately before they became pupæ, prevented the inner
membrane of their intestines from being rejected, as it would have been if
no extraordinary cause had prevented it, attached to the hard excrement. He
found this membrane converted into a jelly occupying great part of the
stomach, which he conjectured was the proximate cause of their death[940].
To conclude this head—spiders are reputed to be subject to the stone: I do
not say Calculus in Vesica; but we are informed by Lesser that Dr. John
Franck having shut up fourteen spiders in a glass with some valerian root,
one of them voided an ash-coloured calculus with small black dots[941].
II. I now come to that class of diseases which appears to prevail almost
universally amongst insects—I mean those resulting from the attack of
parasitic enemies. Thus millions and millions annually perish before they
have arrived at their perfect state. Diseases of this kind proceed either from
vegetable or animal parasites. I shall begin with the first, which will not
occupy us long.
i. As insects pass often no small portion of their life in a state of torpidity, in
which they remain chiefly without motion, it will not seem wonderful,
should any partial moisture accidentally accumulate upon them, that it

affords a seed plot for certain minute fungi to come up and grow in.
Persoon observes with regard to his genus Isaria, that one species grows
upon the larvæ of insects (I. truncata), and another upon pupæ (I.
crassa[942]):—as he does not say upon dead larvæ and pupæ, as upon a
former occasion[943], perhaps in these cases these plants may constitute an
insect disease; but I lay no stress upon it, and only mention the
circumstance here as connected with the history of these animals. Mr.
Dickson has described a Sphæria under the name of entomorhiza that grows
upon dead larvæ; it has a slender long stipes and spherical granulated head:
on the pupa of a species of Cicada in my cabinet, another kind of Sphæria,
with a twisted thickish stipes and oblong head, springs up in the space
between the eyes. I observed something similar but longer, in the grub of
some large beetle in M. Du Fresne's museum at Paris; and I have a
memorandum of having noticed something of the kind on the rostrum of a
Calandra. Bees and humble-bees have been sometimes thought to have
some species of mucor or other Fungilli occasionally growing upon them;
but Mr. Brown is of opinion that stamina which they have filched from
flowers have been mistaken for these Fungilli, since he has detected those
of Orchideæ in some of this tribe, and upon a beetle shown to him by Mr.
MacLeay, one which he knew to be the stamen of an Aristolochia. I once
observed a bunch of what I mistook for a singular mucor that adorned the
vertex of a humble-bee, between the antennæ, which doubtless were of the
same description; and I even saw one upon its wing. Upon a former
occasion I mentioned a parallel circumstance with respect to a species of
Xylocopa[944].
ii. The animal parasites that infest insects are either themselves insects; or
worms.
1. Their insect infesters, as far as we know at present, are confined to the
Orders Strepsiptera, Hymenoptera, Diptera, and Aptera: they attack them
sometimes in their egg state, most frequently when they are larvæ,
occasionally when pupæ, and very rarely in their perfect state. Upon many
of these I have formerly enlarged[945], and I shall now add such further
circumstances as I then omitted. The Strepsiptera Order, as at present
known, consists only of two genera, Stylops and Xenos; the first being
appropriated to the imago of Andrena, a kind of bee, and the latter to that of

the wasps. Their eggs appear to be deposited in the abdomen of these
insects in which they feed, till having attained their full growth they
perforate the membrane that connects its segments; and at the proper time
their pupa-case bursts, they emerge, and take their flight. Sometimes four or
five infest a single bee. Whether the latter dies upon their quitting it I have
not been able to ascertain, but from their flying, when the little parasite is
very near leaving them, with their usual activity, it should seem that this
disease is not mortal; but it probably prevents their breeding: I do not
recollect observing the exuviæ of one in a male bee[946].
The great body of insect parasites, however, belong to the Hymenoptera
Order, and chiefly to the Linnean genus Ichneumon. The insects of this
order have been denominated Principes, because of the wonderful instincts
of ants, wasps, bees, and other gregarious tribes that belong to it; and they
merit a name of honour not less for the benefits that they confer upon
mankind, by keeping within their proper limits the various insect-destroyers
of the produce of the globe. It deserves notice that when these latter
increase to a degree to occasion alarm, their parasites are observed to
increase in a much greater, so as to prevent the great majority of them from
breeding[947]. Though these benefactors of the human race constitute
numerous genera, at present not well ascertained, I shall speak of most of
them under the common name of Ichneumon.
The appearance of these little four-winged flies puzzled much the earlier
naturalists:—that a caterpillar usually turning to a moth or butterfly should
give birth to myriads of flies, was one of those deep mysteries of nature
which they knew not how to fathom[948]: even the penetrating genius of our
great Ray, though he ultimately ascertained the real fact[949], was at one
time here quite at fault; for he seems at first to have thought, when from any
defect or weakness nature could not bring a caterpillar to a butterfly, in
order that her aim might not be entirely defeated, that she stopped short, and
formed them into more imperfect animals[950].
Before I detail more particularly the proceedings of Ichneumons, I shall
make a few general remarks upon them. The structure of the instrument by
which they are enabled to deposit their eggs in their appropriate station has
been before sufficiently described[951]; it is long or short according to the

situation and circumstances of the larva which receives them: if this lives in
the open air, and the access to it is easy, it is usually short and retracted
within the body; but if it lies concealed in deep holes or cavities, or shuns
all approach, it is often very long. Thus in Pimpla Manifestator, which
commits its eggs to the grub of a wild bee inhabiting the bottom of deep
holes bored in posts and rails, the ovipositor is nearly an inch and half in
length, and in some extra-European species three inches. How the egg is
propelled so as to pass in safety from the oviduct, along this extended and
very slender instrument to the grub for which it is destined, has not been
certainly ascertained: but from an observation of Reaumur's[952] it should
seem that it is aided in its passage by some fluid ejected at the same time
with it, or is so lubricated as to slide easily without being displaced. The
flies we are speaking of, by some authors are called Muscæ vibrantes,
because when searching for the destined nidus of their eggs their antennæ
vibrate incessantly, and it is by the use of these wonderful organs that they
discover it wherever it lurks. Bergman observed that Fœnus Jaculator
searches for the latent grub of certain bees and other Hymenoptera with its
antennæ[953]: and from Mr. Marsham we learn that Pimpla Manifestator,
before it inserts its ovipositor in the nest of the grub of Chelostoma
maxillosa, explores it first with one antenna and then with the other,
plunging them all the while intensely quivering up to the very root[954].
With respect to their size, Ichneumons vary greatly; some being so
extremely minute as to be invisible to the naked eye, unless moving upon
glass; while others, as to their length, emulate the giants amongst insects.
The former, unless appropriated to the eggs themselves, usually commit
many eggs to a single larva, while the latter are directed by their instinct to
introduce into them only one. Some of the former description are endowed
with the faculty of leaping[955]. The food of Ichneumons, and indeed of
other internal parasites, is chiefly the epiploon or fat of the larva, but they
never touch any vital organ; so that it continues to feed, and probably more
voraciously, grow, cast its skin, and often it changes to a chrysalis, although
at the same time inhabited by an army of these little devourers.
Ichneumons, as far as has been at present ascertained, are parasitic upon
other insects chiefly in their three first states, a solitary instance only having
been observed of their inhabiting an imago; but from their first exclusion as
eggs from the ovary till their assumption of that state they give them no

rest. I shall therefore first treat of those that infest the eggs; next those
appropriated to larvæ; and lastly those that devour pupæ.
Vallisnieri appears to have been the first naturalist who discovered that
Ichneumons were appropriated to the eggs of other insects. He observed
one proceed from those of the emperor-moth (Saturnia Spini): finding two
holes in each egg, one larger than the other, he conjectured that one was
made when it entered, and the other when it emerged. In this case the egg of
the Ichneumon must be fixed on the outside of the egg it was to feed upon;
though some appear to pierce it with their ovipositor, and consequently
introduce their egg within: for he says afterwards; "I have seen with my
own eyes a certain kind of wild flies deposit their eggs upon other eggs, and
bore and pierce others with an aculeus—by which they have introduced the
egg[956]." Count Zinanni, a correspondent of Reaumur's, saw an Ichneumon
pierce the eggs with her ovipositor repeatedly; which in about fifteen days
were filled with the pupa, and in six more produced the imago[957]. I.
Ovulorum L. is the only known species of egg-devourers; but most likely
there are many, varying in size, according to the size of the egg they inhabit.
Probably I. Atomus L., and I. Punctum Shaw, are of this description[958]. It
is wonderful what a number these little flies destroy:—out of a mass of
more than sixty eggs which was brought to De Geer, not one had escaped
the Ichneumon[959]. But the most extraordinary thing is, that even these
little creatures we are told are destroyed by another still more minute[960].
Though the animals we are speaking of usually destroy only a single egg,
yet some appear not so to confine themselves. Geoffrey informs us that the
larva of one of the Ichneumons whose females are without wings (Cryptus)
devours the eggs of the nests of spiders, and from its size—it is nearly a
quarter of an inch long—it must require several of them to bring it to
maturity[961]. One of those also which destroys the gnat infesting the wheat
(I. inserens) appears to devour them in their egg state, and could not be
brought to perfection by the food that a single one would furnish[962].
The Ichneumons that are parasitic upon larvæ are the most numerous of all.
Some of them are deposited by the parent fly on the outside of their prey,
and others introduced into its interior. Ophion luteum is one of the former
tribe; it plants its eggs in the skin of the caterpillar of the puss-moth

(Cerura Vinula). Each egg is furnished with a footstalk terminating in a
bulb[963], which is so deeply and firmly fixed that it is impossible to extract
it without detaching a portion of the animal with it, and even when the
caterpillar changes its skin it is not displaced. After it is hatched, the grub,
while feeding, keeps its posterior extremity in the egg-shell, to which it
adheres so pertinaciously, that it is scarcely possible to disengage it without
crushing it. It fixes itself by its mandibles to the skin of the caterpillar, and
keeps constantly sucking the contents of its body till it dies: sometimes nine
or ten of these larvæ inhabit a single caterpillar[964]. Reaumur has given an
account of other external Ichneumons. Upon one caterpillar that he
examined, they were so numerous as to render the poor animal quite a
spectacle, and they underwent their metamorphosis attached to it[965]. One
species of this description avenges the cause of insects upon their most
pitiless foes, the all-devouring spider—for in the midst of her toils and lines
of circumvallation it makes her its prey. De Geer, meeting one day with a
young spider of a common kind, observed with surprise, engaged in sucking
it, a small white grub, which was firmly attached to the abdomen near the
trunk. Putting it by in a glass, after some days he examined it again; when
he observed that it had spun the outline of a vertical web, had stretched
threads from the top to the bottom of the glass and from one side to the
other, and had also spun the radii that meet in the centre, and this was all;—
but what was remarkable, the larva that had fed upon it was suspended in
the centre of this web, where it was engaged in spinning its own cocoon,
while the spider, exhausted by this last effort, had fallen dead to the bottom
of the glass. It cannot be asserted positively that this suspension of the larva
of the Ichneumon in the centre of the web always takes place; but if it does,
as seems most probable, it shows that this little parasite is endowed with an
instinct which causes it so to act upon the spider as may induce it to spin a
web so nicely timed as to be sufficiently complete at the period of its death
and of the change of the Ichneumon, for the latter to cast it down and
assume its station[966].
But the great bulk of the parasitic Hymenopterous devourers of larvæ have
their assigned station within the body. As Entomologists in breeding insects
have paid their principal attention to Lepidoptera, it necessarily follows that
their Ichneumon infesters must be most generally known; but doubtless the
larvæ of the other Orders are not wholly liberated from this scourge: they

also require to be kept within due limits, and have their appropriate
parasites. Some, however, in most of them have been detected: of which I
shall now proceed to state to you the most interesting examples, beginning
with the Coleoptera.

Alysia Manducator[967], remarkable for having mandibulæ that do not close,
and toothed at the end, usually attends masses of dung, both of man and
cattle, probably for the purpose of depositing its eggs in some of the
Coleopterous larvæ that inhabit it. Mr. Stephens, one of the most accurate
observers as well as one of the best Entomologists of the present day,
informs me that he once captured three specimens of Timarcha tenebricosa,
from each of which forty or fifty minute Ichneumons emerged. An insect
also of this Order, that is a great benefactor to mankind, as a destroyer of
the plant-lice,—I mean the lady-bird (Coccinella), in its larva state is itself
subject to the attack, as we learn from De Geer, of one of these small
parasites[968]. He detected them also in that of two species of weevils: and
in the pupa of some large grub of a beetle inhabiting the wood of the elm,
perhaps that of the stag-beetle, he found the pupa of one of those
Ichneumons that have an exserted ovipositor[969]. Doubtless, did we know
their history, we should find that numberless species have their internal
assailants belonging to this tribe.
Orthopterous larvæ seem not to have been yet announced as affording a
pabulum to these animals: but the late Dr. Arnold, whose tact for
observation with regard to the manners and economy of insects has
rendered his loss irreparable, discovered that the remarkable parasitic genus
Evania was appropriated to the all-devouring Blatta. Whether it attacked it
in its egg or larva state I have not been informed. This little benefactor is
here extremely rare, at least in the country; perhaps in towns, where the
cock-roach abounds, it may be more common.
The observations of naturalists have chiefly been confined to the
Hemipterous genus Aphis; but these early attracted their notice.
Leeuwenhoek has given a particular and entertaining account of the
proceedings of I. Aphidum. As soon as the little flies approached their prey,
they bent their abdomen, which is rather long, between their legs, so that
the anus projected beyond the head; then with their ovipositor they pierced
the body of the Aphis, at the same time carefully avoiding all contact with it

in every other part: whenever they succeeded in their attempt, a tremulous
motion of the abdomen succeeded. Only a single egg is committed to one
Aphis: when hatched, the latter becomes very smooth and appears swelled;
it is, however, full of life, and moves when touched. Those that are thus
pricked separate themselves from their sound companions, and take their
station on the underside of a leaf. After some days the inclosed grub pierces
the belly of the Aphis, and attaches the margin of the orifice to the leaf by
silken threads; upon this it dies, becomes white, and resembles a brilliant
bead or pearl[970]. De Geer observed also an Ichneumon on the Coccus of
the elm, I. Coccorum[971].
Amongst the Neuropterous tribes likewise, probably the Ichneumonidæ
commit their usual ravages; but their exploits, as far as I recollect, have met
with no historian. I have a small species related to Chelonus, which a
memorandum made when I took it tells me was obtained from Æshna
viatica; yet I do not remember ever tracing that species to its final change,
so that I must have taken this Ichneumon from the perfect insect. It suffices,
however, to prove that this tribe is also exposed to the attack of these
parasites. Where larvæ and pupæ are aquatic, it seems probable, if any
attack is made upon them, that it must take place after they have quitted the
water.
In the Hymenoptera Order itself, almost every genus has been ascertained
to have its Ichneumon parasites. Not even the fortified habitations of the
gall-flies (Cynips) can escape them, almost every species becoming their
prey; a circumstance which puzzled not a little some of the older naturalists,
when they at one time saw a fly not remarkable for its colours or brilliancy
emerge from the curious moss-like Bedeguar of the wild rose, and at
another were struck by the appearance of one of those splendid minims of
nature which almost dazzle the sight of the beholder[972]. Immunity,
however, from this pest seems to have been granted to the gregarious
Hymenoptera; at least none has yet been discovered to attack the ant, the
wasp, the humble-bee, or the hive-bee; in which last, had there been one
appropriated to it, it could never have escaped the notice of the Reaumurs
and the Hubers. The solitary bees, however, as we have seen above[973], do
not escape; and Epipona spinipes, a solitary wasp which feeds its own
young with a number of green caterpillars[974], is itself, when a larva,

though concealed in a deep burrow, the prey of the grub of an Ichneumon,
which by means of a long ovipositor introduces its egg into its body[975].
Even these parasites, whose universal office it is in their first state to prey
upon insects, are themselves subject to the same malady. Ichneumonidan
devourers are kept in check by other Ichneumonidan devourers. These in
some cases are so numerous as to destroy the tithe of the kinds they
attack[976]. Thus an ever-watchful Providence prevents these parasites from
becoming so numerous as to annihilate in any place the species necessary
for the maintenance of the general economy and proportion of animal and
vegetable productions. Amongst the assailants of the Hymenoptera, none
seem to have a more laborious task assigned them than those that pierce the
various galls in which the larvæ of the Cynips tribe are inclosed. To look at
an oak-apple, we should think it a work of difficulty, requiring much
sagacity and address, for one of our little flies to discover the several
chambers lurking in its womb, and to direct their ovipositor to each of them.
Its Creator, however, has enabled it instinctively to discover this, and
furnished it with an appropriate elongated instrument, which will open a
way to the deep and hidden cells in which the grubs reside, penetrate their
bodies, and to each commit an egg. When it prepares to perforate the gall,
the Ichneumon begins by depressing this organ, that it may extricate it from
its sheath; it next elevates its body as high as possible, and bending the
instrument till it becomes perpendicular to the body and to the gall, so as to
touch the latter with its point, it then gradually plunges it in, till it is quite
buried[977]. A very remarkable Hymenopterous parasite (Leucospis), which
when unemployed turns its ovipositor over the back of its abdomen, so that
its end points to its head, is said to deposit its eggs in the nest of the mason-
bee, most probably in the larva: but the curious observations that are stated
to have been made by M. Amédée Lepelletier upon its history have not yet
been given to the public[978].
Dipterous insects, likewise, do not escape from these pests of their Class:
but few observations, however, have been recorded as to the species
assailed by them. We learn from De Geer, that a gnat (Cecidomyia
Juniperi), which forms galls upon the juniper is devoured by an external
Ichneumon[979]; that which injures the wheat in the ear, whose ravages I
formerly mentioned to you[980], affords food to three of these parasites,—
one I lately mentioned as probably devouring its eggs; another pierces the

glumes of the floret, where its destined prey is concealed; and the third
enters it. I once placed a number of the larvæ of the gnat upon a sheet of
paper, at no great distance from each other, and then set down one of these
last Ichneumons in the midst of them. She began immediately to pace
about, vibrating her antennæ very briskly: a larva was soon discovered,
upon which she fixed herself, the motion of her antennæ increasing
intensely; then bending her abdomen obliquely under her breast, she
inserted her ovipositor, and while the egg was depositing these organs
became perfectly motionless. The larva when pricked gave a violent
wriggle. This operation was repeated with all that had not already received
an egg, for only one is committed to each larva. I have often seen it mount
one that was already pricked, but it soon discovered its mistake, and quitted
it untouched[981]. The Hessian Fly also (Cecidomyia Destructor) related to
the preceding, whose alarming ravages I formerly described to you[982], has
a peculiar parasite attached to it, which keeps it in check. The only other
Dipterous insects that I have seen mentioned as affording pabulum to an
Ichneumon, are—one of the aphidivorous flies mentioned by De Geer, who
does not note the species, to the larva of which the Ichneumon commits
only a single egg, producing a grub that intirely devours its interior[983];—
and two described by Scopoli, one, the larva of a fly frequenting hemp; and
the other, which feeds on a Boletus, that of a gnat[984].
The Lepidoptera, however, is the Order over the larvæ of which the
Ichneumons reign with undisputed sway; attacking all indiscriminately,
from the minute one that forms its labyrinth within the thickness of a leaf,
to the giant caterpillar of the hawk-moth. The most useful of all, however,
the silkworm, appears at least with us, exempted from this scourge. De
Geer, out of fifteen larvæ that were mining between the two cuticles of a
rose-leaf, belonging to the first tribe here alluded to, found that fourteen
were destroyed by one of these parasites, only one coming forth to display
itself in all its brilliancy and miniature magnificence[985]. One of the most
useful to us is that which destroys the clothes-moth, which the same writer
also traced[986]. Another, equally serviceable, takes up its abode in the
caterpillar that ravages our cabbages and brocoli (Pontia Brassicæ) which
perish by hundreds from its attacks. As this falls frequently under our
notice, it will not be uninteresting to give a fuller account of it. Reaumur
has traced and related its whole history. One of these little flies that he

observed, was so intent upon the business in which she was engaged, that
she suffered him to watch her motions under a lens, without being
discomposed. She pursued nearly the same plan of proceeding with that of
the Ichneumon of the wheat-gnat just described; except that she repeated
her operations frequently on the same caterpillar in different parts,
alternately plunging in and extracting her ovipositor. She seemed to prefer
the spot where the segments of the body are united, particularly where the
eighth meets the ninth, and the ninth the tenth. When the fly had completed
its work and quitted the caterpillar, Reaumur gave it food, and it did not
seem less lively and vigorous than others of its kind; in less than a fortnight
it assumed the pupa; and in four days the whole of its interior being
devoured, it died: but its parasites, perhaps not finding a sufficient supply of
nutriment in it, never came to perfection[987]. Sometimes, however, these
little grubs arrive at maturity before the caterpillar has become a chrysalis,
when they pierce the skin and begin to emerge. First appears a little white
tubercle, which gradually elevates itself in a direction perpendicular to the
body; while this is doing, a second appears in another place; and so on, till
fifteen or sixteen are seen on each side, giving the caterpillar a very
grotesque appearance. By the alternate contraction and relaxation of their
bodies the grubs effect their complete liberation, which takes place with
respect to the whole in less than half an hour. When entirely disengaged,
they place themselves close to the sides of the caterpillar: even before this
they begin spinning, and draw unequal threads in different directions, of
which they form a cottony bed, which serves as the base of the separate
cocoon of each individual, which they next construct of a beautiful silk
thread of a lovely yellow, which, if it could be unwound and in sufficient
quantity, would yield a silk unrivalled in lustre and fineness[988].
De Geer has recorded a very singular fact which deserves your notice. An
Ichneumon, appropriated to one of the Tortrices, had deposited its eggs in
two of their caterpillars; each produced a considerable number; but those
that emerged from one were all females, and those from the other,
males[989]. He observed a similar fact take place with Misocampus
Puparum[990]. One might conjecture from this circumstance, that as in the
queen-bee[991], so in these Ichneumons, the eggs producing the two sexes
were arranged separately in the ovaries. Reaumur has related, that in one

instance three or four males were produced to one female; and in another
four or five females to one male[992].

But though the great majority of insects are subject to this Scolechiasis[993]
in their larva state, yet sometimes they are not attacked by the Ichneumon
till they have become pupæ. Of this kind is one just mentioned (M.
Puparum), which commits its eggs to the chrysalis of the butterfly of the
nettle, Vanessa Urticæ: the moment this caterpillar quits its skin to assume
that state, while it is yet soft they pierce it and confide to it their eggs[994].
De Geer and others have supposed that this same Ichneumon attacks the
Cocci and Coccinellæ[995]; but this probably is an erroneous supposition.
Cryptus Compunctor also attacks the pupæ of butterflies[996].
If we consider the great purpose of Providence in giving being to this tribe
of destroyers—the keeping of insects within their proper limits,—we may
readily conceive that this purpose is more effectually answered by
destroying them in their preparatory than in their ultimate state, since at
that time the laying of their eggs and a future progeny could not so
effectually be prevented;—this will account for there being few or no
Ichneumons appropriated to them in their latter state.
The next tribe of insect parasites are to be found in the Diptera Order. The
species that has been particularly noticed as such is the Tachina Larvarum;
its larva is polyphagous, laying its eggs upon the bodies of caterpillars of
different kinds. Sometimes a pair is placed on the first segment, sometimes
on the head itself, and sometimes near the anus. These eggs are very hard,
convex, of an oval figure, polished and shining like a mirror. They are fixed
so firmly that if you attempt to remove them with a penknife the skin comes
off with them. When hatched, they enter the body and feed on the interior,
and, undergoing their metamorphosis within it, do not emerge till they enter
their perfect state. The caterpillar thus attacked lives long enough to spin its
cocoon, when it dies[997]. Sometimes, however, these animals quit their prey
sooner. Reaumur saw a grub of one of the Muscidæ come out of a
caterpillar, and then become a pupa, which was so large that he wondered
how it could have been contained in the animal it had quitted[998].
We have now done with those parasites that produce in insects the disease I
have called Scolechiasis[999]: the rest, which belong to the Aptera Order,

will afford us examples both of Phthiriasis and Acariasis[1000].
I begin with the first. Mr. Sheppard once brought me a specimen of a bird-
louse (Nirmus) which he took upon a butterfly (Vanessa Io): and should
such a capture be more than once repeated, it would afford a certain
instance of the first of these diseases amongst insects;—but most probably
the specimen in question had dropped from some bird upon the butterfly.
The only remaining animal belonging to the apterous hexapods that is
parasitic on insects, is by many supposed to be the larva of a giant-beetle
(Meloe Proscarabæus). I have before alluded to this animal[1001], and shall
now resume the subject. Gœdart, Frisch, and De Geer, observed that it
deposited in the earth one or two considerable masses, containing an
infinite number of very minute orange-coloured eggs adhering to each
other, which in about a month were hatched, and produced a number of
small hexapods distinguished by two pairs of anal setæ and a proleg, by
means of which they could move readily upon glass, as I have myself seen:
these little animals precisely corresponded with one found by the latter
author upon Eristalis intricarius; and when that fly was placed amongst
them, they immediately attached themselves to it, so as to leave no doubt of
their identity[1002]. A congenerous species had been detected upon wild
bees, and described by Linné under the name of Pediculus Apis. De Geer is
so thoroughly to be depended upon for his veracity and accuracy of
observation, that we cannot suppose there is any incorrectness in his
statement. If the mass of eggs be, as he represents it, of the size of a hazel-
nut, it must have been the product of a very large insect: in confirmation of
this opinion it may be further observed, that the larva of the kindred genus
Cantharis agrees with it in having anal setæ, though it appears to differ in
having only two conspicuous segments in the trunk[1003]. Those which
infest wild bees make their first appearance upon acrid plants, which the
Meloe likewise feeds upon; from whence with wonderful agility they leap
upon the Andrenæ, &c. that visit these flowers. Strong, however, as all these
facts appear, still we cannot help exclaiming with the illustrious Swede last
named, Who could ever have imagined that the larva of this great beetle
would be found upon the body of flies,—and we may add, or bees? Who
could ever imagine that it would feed like a bird-louse and resemble it so
closely? that in the insertion of its palpi it should exhibit a character
exclusively belonging to that tribe[1004]? Another circumstance seems to

indicate that these hexapods at the time that they take their station in bees or
flies are perfect insects—they do not vary in size, at least not materially.
Where, we may also ask, if they are to become large beetles, where do they
take their principal growth? It cannot be as parasites on the little bees or
flies that they are usually found upon; they must soon desert them, and like
their kindred blister-beetles, as is most probable, have recourse to vegetable
food. What an anomaly in rerum natura! It is much to be wished that some
skilful insect-anatomist would carefully dissect the Meloe; or perhaps by
digging round the roots of the ranunculuses and other acrid plants the larva
of that beetle might be discovered in a later stage of growth, and so this
mystery be cleared up. I should observe here, that Scopoli has described
three parasites as Pediculi; viz. P. rostratus, coccineus, and Cerambycinus;
the first of which Fabricius has adopted under the name of P. Gryllotalpæ,
but which are all evidently hexapod Acarina[1005].
Acariasis seems a disease almost as universal amongst insects as
Scolechiasis; with this difference however, that Acari most commonly take
their station upon them in their perfect state. You have doubtless often
observed the common dung-beetles (Geotrupes) covered on the underside
of their body with small mites (Gamasus Coleoptratorum) which look as if
they were engaged in suction—they are often so numerous that no part is
uncovered; they also attack other beetles[1006], and are sometimes found on
humble-bees. They are easily disturbed, run with great swiftness, and may
often be seen in hotbeds and fermenting dung prowling in search of the
stercorarious beetles. But the most remarkable insect of this kind is the
Uropoda vegetans: it derives its nutriment from the insects it assails not by
its mouth, but by means of a long anal pedicle by which it is attached to
them. De Geer found these in such numbers upon a species of Leptura, that
its whole body was almost covered with them; they hung from the legs and
antennæ in bunches, and gave the animal a most hideous and disgusting
appearance. Under this load of vermin it could scarcely walk or move, and
all its efforts to get rid of them were in vain: many were attached to its body
and to each other by their anal pedicles, but others had cast them off and
were walking about. When put into a glass with earth, they began to
abandon their prey, so that in a few days it was quite freed from its plagues.
He found that these parasites lived long in alcohol[1007].

If you inquire—How are these mites originally fixed by their pedicles? it
seems most probable, that as the Hemerobii, when they lay their eggs, know
how to place them upon a kind of footstalk, so the parent Uropoda has the
same power; and this pedicle appears to act the part of an umbilical chord,
conveying nutriment to the fœtus not from a placenta, but from the body of
the insect to which it is attached; till having thus attained a certain maturity
of growth and structure, it disengages itself and becomes locomotive. Many
eggs of the aquatic Acarina (Hydrachna, &c.) are also furnished with a
short pedicle by which they are fixed to Dytisci and other water insects. De
Geer found some of this description on the underside of the water-scorpion,
so thickly set as to leave no void space: they were oval, of a very bright red,
and of different sizes on different individuals; whence it was evident that
they grow when thus fixed: when hatched or released—for perhaps they
may be regarded as fœtuses in their amnios rather than eggs—they cease to
be parasitical. Let us admire on this occasion, (piously observes this great
Entomologist,) the different and infinitely varied means by which the
Author of Nature has endowed animals, particularly insects, for their
propagation and preservation: for it is a most extraordinary sight to see eggs
grow, and pump as it were their nutriment from the body of another living
animal[1008]. As these mites are fixed to the crust as well as its
inosculations, they must have some means of forcing their nutriment
through its pores.
Another insect, remarkable for its resemblance in some respects to the
scorpion—called in this country the book-crab (Chelifer cancroides), from
its being sometimes found in books—occasionally is parasitic upon flies,
especially the common blue-bottle-fly (Musca vomitoria). They adhere to it
very pertinaciously under the wings; and if you attempt to disturb them,
they run backwards, forwards, or sideways, with equal facility.
Spiders also are infested by mites. Mr. Briggs once found a very small
Theridion, to the thorax of which were attached four oblong bright scarlet
mites, each of which was as large as the thorax itself. He afterwards met
with another spider still smaller, attacked by two of these swoln parasites,
one of which appeared to him nearly equal to the spider in size. This mite
was probably either Leptus Phalangii, or Astoma parasiticum.

2. We now come to a perfectly distinct tribe of insect parasites, which
belong to that section or order of intestinal worms which Rudolph has
denominated Entozoa nematoidea, and Lamarck Vers rigidules[1009]. To this
tribe belong the Gordius of Linné and the Filaria of modern zoologists,
which from the experiments and observations of De Geer, Dr. Matthey, &c.
appear to have been too hastily separated, being really congenerous, and
living indifferently in water and in the intestines of insects and other
animals[1010]. To this genus belong the guinea-worm (Gordius
medinensis[1011]), the Furia infernalis, and several others that are found in
various vertebrate animals. These little worms have been discovered in
insects of almost every Order; and their attack generally produces the death
of the animal, though they appear not to devour those parts that are essential
to life[1012]. I once took a specimen of Pœcilus azureus, and upon
immersing it in boiling water I was surprised to see what at first I mistook
for an intestine, thrust itself forth; but upon a nearer inspection, to my great
surprise I found it was one of these worms, thicker than a horse-hair and of
a brown colour. Mr. W. S. MacLeay also once found one in Abax Striola. It
still remains in my specimen, making it appear as if it had a long tail. De
Geer long ago found these worms in grasshoppers[1012]; but Dr. Matthey has
given the fullest account of one which infested Acrida viridissima. A friend
of his noticing one of these insects which had not strength enough to leap
and could scarcely even walk, being struck with the circumstance, caught
the animal, upon which its hind legs were immediately detached from it.
His surprise was greatly increased when he saw issue from its body a
cylindrical worm about two feet and a half in length. Upon being called, Dr.
M. soon recognised it for a Gordius or Filaria; and on his putting it into
water, it moved in it with great velocity, twisting its long and slender body
in all directions. Upon opening the body of the grasshopper, nothing
appeared within it but the intestine shrunk up to a thread. A few days after,
another was brought, which appeared in full vigour, but its abdomen was
enormously distended, and from it another worm was extracted, which
remained without motion rolled in a spiral direction: intending to preserve
this in spirits of wine—as it had become flat he first immersed it in water,
that it might recover if possible its cylindrical form. Upon immersion a
movement took place in the animal, and it gradually recovered its
plumpness; but it still remained without motion, as if dead, for nearly five

days, when another living specimen being brought and placed with it, as
soon as water was poured on them, the seemingly dead one began to show
by a slight oscillation in its extremities that life was not extinct in it. Fresh
water being poured upon it, at the end of the day it had recovered all its
strength and agility. He afterwards often repeated the same experiment with
a similar result[1013]. From this account it appears that the Gordius or
Filaria has a property resembling that of the Vibrio Tritici, so well
described and so beautifully figured by M. Bauer[1014], of apparently dying
and being resuscitated by immersion in water. How long it can retain this
property remains to be ascertained.

De Geer states that he had seen them of the length of two feet[1015]; but they
vary considerably in this respect. In ants, in which Gould detected them, he
states their length to be not more than half an inch[1016]. In caterpillars,
which they sometimes infest, they are longer; in that of Notodonta Ziczac,
De Geer found one three inches and a half long[1017]; and Rösel three, of six
inches, in that of Deilephila Euphorbiæ[1018]; and in Phalangium cornutum,
according to Latreille, they extend to more than seven inches[1019]. In the
larva of a Phryganea L. the author first named found one which was more
than a foot long, corresponding exactly with the Gordius aquaticus of
Linné; being forked at one extremity, brown above, gray below, and black
at each end[1020]. These animals appear to die as soon as they leave the
body[1021] they have preyed upon; except this happens in water, when their
activity has no repose. In this element they give their bodies every possible
inflexion, often tying themselves in knots in various places, interlacing and
twisting themselves in a hundred different ways; so that when confined in
the body of an insect, from their extreme suppleness and power of
contortion they find sufficient space wherein to pack their often enormous
length[1022]. Linné makes one of their habitats clay; and Mr. W. S. MacLeay
finds them very common at Putney in clay at the bottom of pools.

Dr. Matthey asks—How does the Gordius get into Acrida viridissima[1023]?
And De Geer—Why do they die after having quitted a caterpillar? and
where do they perpetuate their species[1024]? These questions, without
further observations, cannot easily be answered. However, it may be
supposed that carnivorous insects, such as Harpali, &c. may swallow them

when found apparently dead in clay, where the water has been evaporated,
or when they have been ejected by other insects; and they may revive in
their bodies, as Dr. Matthey found them to do in water. It is not difficult to
conjecture that the larvæ of Phryganeæ may meet with them when young in
the water, and sometimes unluckily swallow them with their food. Why
they become as dead when they emerge from their prey we cannot at
present conjecture; but no doubt to answer some wise purpose;—in rainy
seasons they probably revive and get into little hollows full of rain-water.
Upon De Geer's last question—How they perpetuate their species—at
present I can offer no conjecture.
I am, &c.

LETTER XLV.
SENSES OF INSECTS.

At first one would think that the senses of insects might be described in
very few words, and scarcely afford matter for a separate letter; but when
we find that physiologists are scarcely yet agreed upon this subject, and that
the use of some of their organs, which appear to be organs of sensation, has
not yet been satisfactorily ascertained—we shall not wonder that it requires
more discussion than at the first blush we were aware of. In treating on this
head I shall first say something on the senses in general, and then confine
myself to those of insects.
Touch, taste, smell, hearing, and sight, I need not tell you, is the usual
enumeration of the senses: but as the term includes every means of
communication with the external world, the list perhaps might be increased;
and there is ground for thinking that the number seven, so signalized as a
sacred number[1025], may also here have place. Dr. Virey, an eminent
physiologist, whose sentiments on various subjects I have before noticed
with approbation[1026], appears to be of opinion that there are really seven
senses; which he divides into those that are altogether physical, and those
that are more connected with the intellect. The first of these divisions
contains four senses,—touch, love, taste, and smell;—the second three,—
hearing, sight, and the internal sense of thought, or the brain[1027]. That he is
right in adding love to the list seems to me evident, because it is as distinct
from touch, as smelling and taste are. With regard to the other, though it
may be expected that there should be a transitive sense connecting the
intellect (if I may so speak) with the external organ of sense, and as a
medium by which the former can receive the notices of the external world
furnished by the latter; yet it seems improper to make the entire brain itself
a sense. We know that the agent between the common sensory and the sense
is the consciousness or perception of the impression. "Seeing we may see
and not perceive, and hearing we may hear and not understand." The
picture may be painted upon the retina of the eye, the sound may strike

upon the tympanum of the ear; but neither the one nor the other be received
by the intellect, unless the internal power or faculty of perception be in
action and mediate between them. This is what I mean by the internal
sense, which, to use a term of Mr. W. S. MacLeay's[1028], is osculant
between intellect and sense, or forms the transit from one group of powers
to the other.
Of the ordinary senses, sight holds the first rank: it can dart to the region of
the stars, and convey by the perceiving sense, to the sensory, ideas of
innumerable objects. Next in rank is hearing, which can receive sounds
from a great distance; but the ideas it remits are confined only to one object,
the variations of tones. In the other organs the sensitive power is much more
confined. There is another difference between the intellectual and physical
senses:—the former are the only ones that receive and convey sensations of
the beautiful and sublime; of harmony and discord,—the latter, though they
minister more to our sensual enjoyments, add little to our intellectual; and
therefore too devoted an indulgence in them debases our nature, and levels
us with the brutes, which use their eyes and ears only for information, not
for pleasure[1029].
In man the ordinary five senses are usually in their greatest perfection,
although in some animals particular senses have a greater range. The
Vertebrates in general are also gifted with the same number, though there
are some exceptions. But in the Invertebrates they are seldom to be met
with all together in the same object. The Cephalopods have no smell.
Several Gasteropods can neither hear nor see. The animals of bivalve shells
have neither eyes, nor ears, nor smell; and the zoophytes and the races
below them have, it is affirmed, only the single sense of touch, which in
them is so extremely delicate as to be acted upon even by light[1030].
Not so our insects. These, there is good reason to believe, possess all the
ordinary senses. That they can see, touch, taste, and smell, no one denies.
Linné and Bonnet, however, thought them deprived of hearing[1031]; but
numerous observations prove the contrary. That they hear in their larva
state, is evident from facts stated by the latter physiologist. He found that
the sound of his voice evidently affected some caterpillars; which he
attributes, but surely without reason, to the delicacy of their sense of touch:
at another time, when some caterpillars of a different species were moving

swiftly, he rang a small bell; upon which they instantly stopped and moved
the anterior part of their body very briskly[1032]. That they possess this
faculty in their imago state is confirmed still more strongly by facts. I once
was observing the motions of an Apion under a pocket microscope: on
seeing me it receded. Upon my making a slight but distinct noise, its
antennæ started: I repeated the noise several times, and invariably with the
same effect. A Harpalus, which I was holding in my hand, answered the
sound in the same manner repeatedly. Flies, I have observed, at brisk and
distinct sounds move all their legs; and spiders will quit their prey and retire
to their hiding places. Insects that live in society give notice of intended
movements, or assemble their citizens for emigration by a certain hum[1033].
But the most satisfactory proof of the hearing of these animals is to be had
from those Orthoptera and Hemiptera whose males are vocal. Brunelli kept
and fed several males of Acrida viridissima (a grasshopper with us not
uncommon) in a closet, which were very merry, and continued singing all
the day; but a rap at the door would stop them instantly. By practice he
learned to imitate their chirping: when he did this at the door, at first a few
would answer him in a low note, and then the whole party would take up
the tune and sing with all their might. He once shut up a male in his garden,
and gave the female her liberty; but as soon as she heard the male chirp, she
flew to him immediately[1034].
But although physiologists are for the most part agreed that insects have the
ordinary five senses of vertebrate animals, yet a great variety of opinions
has obtained as to their external organs; so that it has been matter of doubt,
for instance, whether the antennæ are for smell, touch, or hearing; and the
palpi for smell, taste, or touch. Nor has the question, as it appears to me,
been satisfactorily decided: for though it is now the most general opinion
that the primary use of antennæ is to explore as tactors, yet by the most
strenuous advocates of this opinion they are owned not to be universally so
employed; so that granting this to be one of their principal functions, yet it
seems to follow that there may be another common to them all, which of
course would be their primary function. We are warned, however, not to lay
any stress upon the argument to be drawn from analogy; and told that we
might as well dispute about the identity of the nose of a man, the proboscis
of the elephant, the horn of the rhinoceros, the crest of the cock, or the beak
of the toucan[1035]. But this is merely casting dust in our eyes: for though

three of these are nasal organs, bearing nostrils; the two others have no
relation to the question, the horn of the rhinoceros and the crest of the cock
being merely appendages, and have no more analogy to the nose and
nostrils, which co-exist with them, than they have to the eyes or ears. I have
on a former occasion observed, that a gradual change sometimes takes place
in the functions of particular organs; but still, generally speaking, this
observation regards secondary functions—the primary usually remaining
untouched. We may say, for instance, with regard to the primary use of the
legs of animals, that it is locomotion; while the secondary is either walking,
running, jumping, flying, or swimming, according to the circumstances and
nature of the animal. Thus the fore-legs of the Mammalia, in birds become
wings, and both pair in fish are changed to fins. Observe, I do not say
always and invariably, but in most cases,—that analogous parts have
analogous uses, at least as far as primary uses are concerned. When,
therefore, we cannot have demonstrative evidence concerning the function
of an organ discoverable in any animal, we may often derive satisfactory
probable arguments from the analogies observable in their structure
compared with that of other animals, concerning the nature of whose organs
we have no doubt. In fact, the chief evidence we have with regard to the
office of the organs of sense in the animals immediately below ourselves, is
that of analogy;—because we see with our eyes, hear with our ears, &c., we
conclude, with reason, that they do the same.
In inquiring therefore into what may be the most general use of the antennæ
of insects, I shall endeavour to discover whether there is any part in the
higher animals to which they may be deemed to exhibit any analogy. And
here I must refer you to what I have said on a former occasion upon the
present subject; where I made it evident, I hope, that the great bulk of the
parts and organs of insects, in this particular differing from the majority of
Invertebrates, are, some in one respect, some in another, and some in many,
really analogous to those of the higher animals[1036]; and that a great many
of them, though varying in their structure, have the same functions. Thus
the analogues of the eyes of Vertebrates are for seeing; of the jaws for
masticating; of the lips for closing the mouth; of the legs for walking, &c.
We have seen also very recently, that a similar analogy, more or less
strongly marked, holds also in their internal organs[1037]; so that it may be
safely affirmed, that if all the invertebrate insects, though gifted with

numerous peculiarities, present the most striking picture of those animals
that have an internal skeleton, and more particularly of the Mammalia,—we
may assume it as a probability, the above circumstances being allowed their
due weight, that where facts do not prove the contrary, the function of
analogous organs is more or less synonymous, though perhaps the structure
and modus operandi may be different.
In the letter lately referred to, I observed that the antennæ of insects are
analogous to ears in Vertebrates[1038]. Their number corresponds; they also
stand out from the head; and what has weighed most with me, unless they
are allowed as such, no other organ can have any pretension to be
considered as representing the ear. If we reflect, that in every other part and
organ, the head of insects has an analogy to that of Mammalia, we must
regard it as improbable that these prominent organs should not also have
their representative. Admitting then that they are the analogues of ears, it
will follow, not as demonstratively certain, but as probable, that their
primary function may be something related to hearing. I do not say direct
hearing, or that the vibrations of sound are communicated to the sensorium
by a complex structure analogous to that of the internal ear in Mammalia—
but something related to hearing. I conceive that antennæ, by a peculiar
structure, may collect notices from the atmosphere, receive pulses or
vibrations, and communicate them to the sensorium, which, though not
precisely to be called hearing, may answer the same purpose. From the
compound eyes that most of them have, the sense of seeing in insects must
be very different from what it is in vertebrate animals; and yet we do not
hesitate to call it sight: but since antennæ, as we shall see, apparently
convey a mixed sensation, I shall have no objection, admitting it as their
primary function, to call it after Lehmann Aëroscepsy[1039]. I lately related
some instances of sound producing an effect on the antennæ of insects: I
will now mention another that I observed, still more remarkable. A little
moth was reposing upon my window; I made a quiet, not loud, but distinct
noise: the antenna nearest to me immediately moved towards me. I repeated
the noise at least a dozen times, and it was followed every time by the same
motion of that organ; till at length the insect being alarmed became more
agitated and violent in its motions. In this instance it could not be touch;
since the antenna was not applied to a surface, but directed towards the
quarter from which the sound came, as if to listen. Bonsdorf made similar

observations, to which Lehmann seems not disposed to allow their proper
weight[1040]. It has been used as an argument to prove that antennæ are
primarily tactors, or instruments of touch, that Fœnus Jaculator, before it
inserts its ovipositor, plunges its antennæ into the hole forming the nidus of
the bee, to the grub of which it commits its egg[1041]. But had those who
used this argument measured the antennæ and the ovipositor of this
ichneumon, they would have discovered that the latter is thrice the length of
the former: and as these insects generally insert it so that even part of the
abdomen enters the hole, it is clear that the antenna cannot touch the larva;
its object therefore cannot be to explore by that sense. Others suppose that
by these organs it scents out the destined nidus for its eggs; but Lehmann
has satisfactorily proved that they are not olfactory organs. We can
therefore only suppose, either that by means of its antennæ it hears a slight
noise produced by the latent grub, perhaps by the action of its mandibles; or
else that by its motions it generates a motion in the atmosphere of its
habitation, which striking upon the antennæ of the Fœnus, are by them
communicated to its sensory. A similar disproportion is observable between
the antennæ and ovipositor of Pimpla Manifestator, before signalized[1042].
Bees, when collecting honey and pollen, first insert the organs in question
into the flowers which they visit; but, as I have more than once observed,
they merely insert the tip of them. If anthers are bursting, or the nectar is
exuding, these processes probably are attended by a slight noise, or motion
of the air within the blossom, which, as in the last case, affects, without
immediate contact, the exploring organs.
If the structure of antennæ be taken into consideration, it will furnish us
with additional reasons in favour of the above hypothesis, with regard to
their primary function. We shall find that these organs, in most of those
insects which take their food by suction, are usually less gifted with powers
of motion, than they are in the mandibulate tribes; so that in the majority of
the Homopterous Hemiptera and Diptera, as is generally acknowledged,
they cannot be used for touch. Under this view, they may be divided into
active antennæ and passive antennæ: of the former, the most active and
versatile are those of the Hymenoptera. By means of them, as was before
observed[1043], their gregarious tribes hold converse, and make inquiry—
frequently without contact—in the pursuit and discharge, if I may so speak,
of the various duties devolved upon them by Providence. Amongst active

antennæ, some are much more complex in their structure than others—a
circumstance which is often characteristic of the male insect[1044]: but if we
examine such antennæ, we shall find that their most sensitive parts cannot
come in contact with the earth or other bodies for exploring their way; but
having thus a greater surface exposed to the action of the atmosphere, they
have more points to receive vibrations, or any pulses or other notices
communicated to it. It is thus, probably, that in their flights, when they
approach within a certain distance, they discover the station of the other
sex. Even the plumose antennæ of male gnats may in some respects thus be
acted upon. In the Lamellicorn beetles, the knob of these organs in both
sexes consists of laminæ, the external ones on their outside, of a corneous
substance; while their internal surface, and the inner laminæ—which are
included between them, as an oyster between the valves of its shell—are
covered with nervous papillæ. If you examine the proceedings of one of
these little animals, you will find before it moves from a state of repose that
its antennæ emerge, and the laminæ diverge from each other; but that it
does not apply them to surfaces to explore its way, but merely keeps them
open to receive notices from the atmosphere. Even simple antennæ are often
employed in this way, as well as for touch. I once noticed a species of
Leptocerus, a trichopterous genus, in which these organs are very long, that
was perched upon a blade of grass; its antennæ vibrated, and it kept moving
them from side to side in the air, as if thus by aëroscepsy it was inquiring
what was passing around it. Dr. Wollaston has an observation bearing so
precisely upon this question, and in general so extremely similar to what is
here advanced, that I must copy it for your consideration. "Since there is
nothing in the constitution of the atmosphere," says he, "to prevent
vibrations much more frequent than any of which we are conscious, we may
imagine that animals like the Grylli, whose powers appear to commence
nearly where ours terminate, may have the faculty of hearing still sharper
sounds, which at present we do not know to exist; and that there may be
other insects, hearing nothing in common with us, but endued with a power
of exciting, and a sense that perceives, vibrations indeed of the same nature
as those which constitute our ordinary sounds, but so remote, that the
animals who perceive them may be said to possess another sense, agreeing
with our own solely in the medium by which it is excited, and possibly
wholly unaffected by these slower vibrations of which we are
sensible[1045]." That insects, however, hear nothing in common with us, is

contrary to fact; at least with respect to numbers of them. They hear our
sounds, and we theirs; but their hearing or analogous sense is much nicer
than ours, collecting the slightest vibratiuncle imparted by other insects, &c.
to the air. In inquiring how this is done, it may be asked—How know we
that every joint of some antennæ is not an acoustic organ, in a certain sense
distinct from the rest? We see that the eyes of insects are usually compound,
and consist of numerous distinct lenses;—why may not their external ears
or their analogues be also multiplied, so as to enable them with more
certainty to collect those fine vibrations that we know reach their sensory,
though they produce no effect upon our grosser organs? I propose this
merely as conjecture, that you may think it over, and reject or adopt it, in
proportion as it appears to you reasonable or the contrary; and in the hope
that some anatomist of insects, who, to the sagacity and depth of a Cuvier
and a Savigny adds the hand and eye of a Lyonet, may give to the world the
results of a more minute dissection and fuller investigation of the antennæ
of these animals, than has yet been undertaken.
But besides receiving notices from the atmosphere, of sounds, and of the
approach or proximity of other insects, &c., the antennæ are probably the
organs by which insects can discover alterations in its state, and foretel by
certain prognostics when a change of weather is approaching. Bees possess
this faculty to an admirable degree. When engaged in their daily labours, if
a shower is approaching, though we can discern no signs of it, they foresee
it, and return suddenly to their hives. If they wander far from home, and do
not return till late in the evening, it is a prognostic to be depended upon,
that the following day will be fine: but if they remain near their habitations,
and are seen frequently going and returning, although no other indication of
wet should be discoverable, clouds will soon arise and rain come on. Ants
also are observed to be excellently gifted in this respect: though they daily
bring out their larvæ to sun them, they are never overtaken by sudden
showers[1046]. Previously to rain, as you well know, numberless insects seek
the house; then the Stomoxys calcitrans, leaving more ignoble prey, attacks
us in our apartments, and interrupts our studies and meditations[1047]. The
insects of prey also foresee the approach of wet weather, and the access of
flies, &c. to places of shelter. Then the spiders issue from their lurking-
places, and the ground-beetles in the evening run about our houses. Passive
antennæ, which are usually furnished with a terminal or lateral bristle, and

plumose and pectinated ones, seem calculated for the action of the electric
and other fluids dispersed in the atmosphere, which in certain states and
proportions may certainly indicate the approach of a tempest, or of showers,
or a rainy season, and may so affect these organs as to enable the insect to
make a sure prognostic of any approaching change: and we know of no
other organ that is so likely to have this power. I say electric fluid, because
when the atmosphere is in a highly electrified state, and a tempest is
approaching, is the time when insects are usually most abundant in the air,
especially towards the evening; and many species may then be taken, which
are not at other times to be met with: but before the storm comes on, all
disappear, and you will scarcely see a single individual upon the wing. This
seems to indicate that insects are particularly excited by electricity[1048].—
But upon this head I wish to make no positive assertion, I only suggest the
probability of the opinion[1049].
From all that has been said, I think you will be disposed to admit that the
primary and most universal function of the antennæ is to be the organs of a
sense, if not the same, at least analogous to hearing, and answering the
same end; something perhaps between it and touch. In some, however, as
has been found in the Crustacea, an organ of hearing, in the ordinary sense,
may exist at the base of the antennæ, which may act the part in some
measure of the external ear, and collect and transmit the sound to such
organ[1050].
That numerous antennæ, as a secondary function, explore by touch, is
admitted on all hands, and therefore I need not enlarge further upon this
point; but shall proceed to inquire whether insects do not possess some
other peculiar organs that are particularly appropriated to this sense. First,
however, I must make some general observations upon it. Of all our senses,
touch is the only one that is not confined to particular organs, but dispersed
over the whole body: insects, however, from the indurated crust with which
they are often covered, feel sensibly, it is probable, only in those parts
where the nerves are exposed, by being covered with a thinner epidermis, to
external action. Not that they cannot feel at all in their covered parts; for as
we feel sufficiently for walking, though our feet are covered by the thick
sole of a boot or shoe, so insects feel sufficiently through the crust of their
legs for all purposes of motion. Besides, the points that are covered by a

thinner cuticle are often numerous; so that touch, at least in a passive sense,
may be pretty generally dispersed over their bodies; but active or exploring
touch is confined to a few organs, as the antennæ, the palpi, and the arms.
The two last I shall now discuss.
Various opinions have been started concerning the use of the palpi.
Bonsdorf thought that they were organs of smell; Knoch, that this sense was
confined to the maxillary ones, and that the labial ones were appropriated to
taste[1051]: but the most early idea, and that from which they derive their
present name of palpi (feelers), is, that they are organs of active touch; and
this seems to me the most correct and likely opinion. Cuvier, himself a host,
has embraced this side of the question[1052], and Lehmann also admits
it[1053]. The following observations tend to confirm this opinion. The palpi
of numerous insects when they walk, are frequently, or rather without
intermission, applied to the surface on which they are moving—this you
may easily see by placing one upon your hand; which seems to indicate that
they are feelers. In the Araneidæ they are used as legs; and by the males at
least, as exciting if they be not really genital organs[1054]. In the
Scorpionidæ they answer the purpose of hands: besides being usually much
shorter than antennæ, they are better calculated to assist an insect in
threading the dark and tortuous labyrinths through which it has often to
grope its way, and where antennæ cannot be employed. I have noticed that
Hydrophili—in which genus the palpi are longer than the antennæ—when
they swim, have their antennæ folded; while the former are stretched out in
front, as exploring before them. As these are attached to the under-jaws and
under-lip, we may suppose they are particularly useful to insects in taking
their food; and upon this occasion I have often observed that they are
remarkably active. I have seen Byturus tomentosus, a beetle which feeds
upon pollen, employ them in opening anthers; and the maxillary pair appear
to me to assist the maxillæ in holding the food, while the mandibles are at
work upon it.
The arms or fore-legs of some insects are also organs of active touch, being
used, as we have seen, for cleaning the head, digging, repairing their
dwellings, and the like[1055]. By the Ephemeræ, which have very short
antennæ, the fore-legs, when they fly, are extended before the head, parallel

with each other and quite united—probably to assist in cutting the air. The
Trichoptera use their antennæ for the same purpose.

Another sense of which the organ seems uncertain is that of smelling, and
various and conflicting opinions have been circulated concerning it.
Christian thought that insects smell distant objects with their antennæ, and
near ones with their palpi[1056]. Comparetti has a most singular opinion. He
supposes in different tribes of insects that different parts are organs of
smell: in the Lamellicorns he conjectures the seat of this sense to reside in
the knob of the antennæ; in the Lepidoptera in the antlia; and in some
Diptera and Orthoptera in certain frontal cells[1057]. At first sight, one of
the most reasonable opinions seems to be that of Baster, adopted by
Lehmann, and which has received the sanction of Cuvier[1058],—that the
spiracles are organs of smell as well as of respiration. Lehmann has
adduced several arguments in support of this opinion. Because we both
respire and smell with our nostrils, he concludes that neither the antennæ
nor any other part of the head of insects can serve for smell, since they are
not the seat also of respiration; and that there can be no smell where the air
is not inspired[1059]. Again, because nerves from the ganglions of the spinal
chord terminate in bronchiæ near the spiracles, they must be for receiving
scents from those openings. Though it was necessary, in the higher animals,
that the organ of scent should be near the mouth, because they are larger
than their food; yet the reverse of this being the case with insects, which
often even reside in what they eat, it is to them of no importance where
their sense of smelling resides[1060]. By exposing antennæ, by means of an
orifice in a glass vessel, to the action of stimulant odours, they appeared
quite insensible to it: but he does not name the result of any experiment in
which he exposed the mouth to this action; nor at all distinctly how the
insect was affected when the spiracles were exposed to it[1061].
But though some of these arguments appear weighty, there are others, I
think, that will more than counterbalance them, making it probable that the

seat of this sense is in the head, either in its ordinary station at the extremity
of what I call the nose, between it and the upper-lip, or under those parts.
That the nose corresponds with the so-named part in Mammalia, both from
its situation and often from its form, must be evident to every one who
looks at an insect[1062]; and when we further consider the connexion that
obtains between the senses of smell and taste, how necessary it is that the
seat of the one should be near that of the other, and that it really is so in all
animals in which we certainly know its organ[1063]; we shall feel convinced
that the argument from analogy is wholly in favour of the nose, and may
thence consider it as probable that the sense in question does reside there.
Lehmann seems to be of opinion, because an insect is usually smaller than
what it feeds upon, that it makes no difference whether it smells with its
head or with its tail: but one would think that a flying insect would be more
readily directed to its object by smelling with the anterior part of the body
than with the posterior; and that a feeding one would also find it more
convenient in selecting its food. As to the argument,—that smell must be the
necessary concomitant of the respiratory openings, and that there can be no
smell where the air is not inspired,—this seems asserting more than our
knowledge of these animals will warrant: for the organs of the other senses,
though the senses themselves seem analogous, are so different in their
structure, and often in the mode in which they receive the impressions from
external objects, that analogy would lead us to expect a difference of this
kind also in the sense of smell. Besides, smell does not invariably
accompany respiratory organs even in the higher animals,—for we breathe
with our mouths, but do not smell with them. Cuvier says that the internal
membrane of the tracheæ being soft and moist, appears calculated to
receive scents[1064]. But here his memory failed him; for it is the external
membrane alone that answers this description; the internal consisting of a
spiral elastic thread, and seeming not at all fitted to receive impressions, but
merely to convey the air[1065]. That nerves penetrate to the bronchiæ, does
not necessarily imply that they are connected with the sense in question,
since this may be to act upon the muscles which are every where
distributed.
I shall now state some facts that seem to prove that scents are received by
some organ in the vicinity of the mouth, and probably connected with the
nose. M. P. Huber, desirous of ascertaining the seat of smell in bees, tried

the following experiments with that view. These animals, of all ill scents,
abominate most that of the oil of turpentine. He presented successively to
all the points of a bee's body, a hair-pencil saturated with it: but whether he
presented it to the abdomen, the trunk, or the head, the animal equally
disregarded it. Next, using a very fine hair-pencil, while the bee had
extended its proboscis, he presented the pencil to it, to the eyes and
antennæ, without producing any effect; but when he pointed it near the
cavity of the mouth, above the insertion of the proboscis, the creature started
back in an instant, quitted its food, clapped its wings, and walked about in
great agitation, and would have taken flight if the pencil had not been
removed. On this, it began to eat again; but on the experiment being
repeated, showed similar signs of discomposure: oil of marjoram produced
the same effect, but more promptly and certainly. Bees not engaged in
feeding appeared more sensible of the impression of this odour, and at a
greater distance; but those engaged in absorbing honey might be touched in
every other part without being disturbed. He seized several of them, forced
them to unfold their proboscis, and then stopped their mouth with paste.
When this was become sufficiently dry to prevent their getting rid of it, he
restored to them their liberty: they appeared not incommoded by being thus
gagged, but moved and respired as readily as their companions. He then
tempted them with honey, and presented to them near the mouth, oil of
turpentine, and other odours that they usually have an aversion to; but all
produced no sensible effect upon them, and they even walked upon the
pencils saturated with them[1066].
These experiments incontestibly prove that the organ of scent in bees—and
there is no reason to think that other insects do not follow the same law—is
in or near the mouth, and above the proboscis. It remains, therefore, that we
endeavour to discover its precise situation: and as insects cannot tell us, nor
can we perceive by their actions, in what precise part the sense in question
resides, the only modes to which we can have recourse to form any
probable conjecture, are analogy and dissection. At first, the opinion noticed
above, that the palpi are its organs, seems not altogether unreasonable; but
as the argument from analogy, except as to their situation near the mouth, is
not in favour of them, and there seems no call, were smell their function, for
the numerous variations observable in their structure, I think we must
consider them, as I have endeavoured to prove, rather as instruments of

touch. Let us now inquire, whether there be not discoverable upon
dissection, in the interior of the head of any insects, some organ that may be
deemed, from its situation, under what we have called the nose and nostrils,
the seat of the sense we are treating of. The common burying-beetle
(Necrophorus Vespillo) is an insect remarkable for its acuteness of smell,
which enables it to scent out and bury, as was formerly related to you[1067],
the carcases of small animals. Take one of these insects, and kill it as
formerly directed,—examine first its nose: in the middle of the anterior part
you will see a subtrapezoidal space, as it were cut out and filled with a paler
piece of a softer and more membranous texture. Next divide the head
horizontally; and under the nose, and partly under this space, which I call
the rhinarium or nostril-piece[1068], you will find a pair of circular pulpy
cushions, covered by a membrane transversely striated with beautifully fine
striæ. These are what I take to be the organs of smell, and they still remain
distinctly visible in a specimen I have had by me more than fifteen years. A
similar organ may be discovered in the common water-beetle (Dytiscus
marginalis), but with this peculiarity, that it is furnished with a pair of
nipples. I have before described an analogous part covered with papillæ, in
Æshna viatica, and you will find it in other insects[1069]. Perhaps at first this
part may seem merely a continuation of the palate; but if you consider the
peculiarities in its structure just noticed, it is evidently a sensiferous organ;
and as the sense of smell appears to reside in the head, this is its most
probable seat. But by what channel scents act upon it,—whether they are
transmitted through the pores of the part representing the nostrils, or
received by the mouth,—I will not venture to assert positively: but from the
circumstance of their being membranous in some insects remarkable for
acute scent, as in Necrophorus, Staphylinus, &c., there seems some ground
for the former opinion, which receives further confirmation from an
observation of an eminent Comparative Anatomist, M. Carus, with respect
to Acrida verrucivora, in which under the nose and rhinarium, as appears
from his description, he found some tracheæ, and two lobes of the cerebral
ganglion, which caused him to regard this as the seat of the sense of
smell[1070]. He also tells us that Rosenthal, in the blue-bottle-fly (Musca
vomitoria) places the sense of smell partly in a delicately folded membrane
observable in its head[1071]. As the sense of smell in these little beings is
extremely acute, as well as their hearing, the perception of odours may

reach their sensory through the above pores; and even those in the hard
rhinarium of an Anoplognathus may receive and transmit them; and besides
the upper-lip and nose are often united by membrane, perhaps representing
the rhinarium, as in Goerius, &c.[1072] which may facilitate such
transmission.

That insects taste, no one hesitates to believe, though some have supposed
the palpi to be the organ of that sense; but as they have a tongue, as we have
shown, we may with Cuvier conclude, that one of its primary functions is to
taste their food[1073]. I shall not therefore launch out further upon this head.
I have now placed before you a picture, or rather sketch, of the insect world.
And whether we regard their general history and economy, their singular
metamorphoses, the infinite varieties and multiplicity of their structure both
external and internal, and their diversified organs both of sense and motion
—I think you will be disposed to own, that in no part of his works is the
hand of an Almighty and All-wise Creator more visibly displayed, than in
these minutiæ of creation; that they are equally worthy of the attention and
study of the Christian Philosopher with any of the higher departments of the
animal kingdom; and that all praise is due to Him, for placing before our
eyes, for our entertainment and instruction, such a beautiful moving picture
of little symbols and agents, perpetually reflecting his glory and working
his will.
I am, &c.

LETTER XLVI.
ORISMOLOGY, OR EXPLANATION OF TERMS.

It was by the language of terms that he invented and employed, as well as
by his system and methods of arrangement, that Linné smoothed the way to
the study of Natural History;—having therefore led you through a large
portion of the flowery fields of the Science of Entomology, I must now
conduct you into that arid but not barren or unprofitable region. To enable
you to understand descriptions of insects, or to describe them yourself, you
must have a knowledge of the technical language by which their parts and
characters are expressed. Much of this you already know from the
definitions of external parts, furnished in a former letter[1074]: I shall now
give you a more full and general explanation of terms, adding many new
ones for unnoticed characters, that may be conveniently employed.

The science of terms, which I shall call Orismology[1075], may be divided
into two branches—General Orismology, and Partial Orismology; the first
containing general definitions, and the last those relating to particular parts
and organs.
A. GENERAL ORISMOLOGY.
I. SUBSTANCE.

. Membranous (Membranacea). A fine, thin, transparent substance. A
Membrane.—Ex. Wings of Hymenoptera and Diptera.
. Pergameneous (Pergamenea). A thin, tough, and less transparent
substance, somewhat resembling parchment.—Ex. The Tegmina of the
Orthoptera[1076].
. Coriaceous (Coriacea). A thicker, flexible substance, resembling leather.
—Ex. Elytra of Telephorus and the Malacodermi.

. Corneous (Cornea). A hard inflexible substance resembling horn.—Ex.
Elytra of Lucanus Cervus and many other Coleoptera.
. Crustaceous (Crustacea). A rigid calcareous substance.—Ex. The Shell
of a Lobster or Crab.
. Callous (Callosa). A substance without pores, harder than the
surrounding matter, and usually elevated above it.—Ex. Elevated parts
of the Collar in Nomada. (Mon. Ap. Angl. Apis * b.)[1077] Spots on the
elytra of Stenocorus (Tylostagmus K. MS.) bimaculatus and affinities.
. Cartilagineous (Cartilaginea). A gristly substance between bone and
ligament.—Ex. The Tongue of many Hymenoptera.
. Subereous (Suberea). A soft elastic substance somewhat resembling
cork[1078]. The galls of some species of Cynips when mature approach
to this substance.
. Spongiose (Spongiosa). A soft elastic substance resembling sponge.—Ex.
The Pulvilli of Thanasimus, Buprestis, &c.
0. Ligneous (Lignosa). A hard unelastic substance like wood.—Ex. Galls
of some species of Cynips.
1. Carnose (Carnosa). A soft, fleshy substance.—Ex. Caterpillars and
Grubs.
2. Tubulose (Tubulosa). When the interior is hollow or empty.
3. Solid (Solida). When the interior is full.

II. RESISTANCE.

. Rigid (Rigida). Hard, which does not bend or yield to pressure.—Ex. The
weevils (Rhyncophora).
. Flexile (Flexilis). Which easily bends, or yields to pressure without
breaking.—Ex. Elytra of Telephorus.
. Soft (Mollis). Flexile and retaining the marks of pressure.—Ex. Elytra of
Meloe.

III. DENSITY.

. Foliaceous (Foliacea). Very thin and depressed, scarcely thicker than a
leaf.—Ex. Aradus corticalis and Coreus paradoxus.
. Depressed (Depressa). When the vertical section is shorter than the
transverse.—Ex. Trogosita mauritanica.
. Compressed (Compressa). When the transverse section is shorter than the
vertical.—Ex. Centrotus cornutus: Abdomen in Cynips.
. Plump (Pinguis). Naturally and proportionably plump.—Ex. Thylacites,
&c. Most of the Cicadæ.
. Obese (Obesa). Unnaturally enlarged and distended, as if from disease or
too much food. Ex. Chrysomela Polygoni ♀ , Galeruca Tanaceti ♀ ,
Brachycerus.
. Ventricose (Ventricosa). Bellying out as if filled with air.—Ex.
Pneumora.

IV. PROPORTION.

. Thick (Crassa). Disproportionably thick throughout.—Ex. Copris.
. Incrassate (Incrassata). Disproportionably thick in part.—Ex. Base of
the Abdomen of Æshna and many Libellulina. Plate IX. Fig. 9.
. Slender (Tenuis). Disproportionably slender throughout.—Ex. Lixus
paraplecticus.
. Attenuate (Attenuata). Disproportionably slender in part.—Ex. Tail of
Scorpio, Raphidia ♂, &c.
. Broad (Lata). Disproportionably broad throughout.
. Dilatate (Dilatata). Disproportionably broad in part.—Ex. Elytra of
Lycus fasciatus, &c. Plate XIII. Fig. 20.
. Narrow (Angusta). Disproportionably narrow throughout.—Ex.
Abdomen of Agrion.

. Angustate (Angustata). Disproportionably narrow in part.—Ex. Elytra of
Sitaris humeralis. Plate XIII. Fig. 19.
. Long (Longa). Disproportionably long throughout.—Ex. Scolopendra.
0. Elongate (Elongata). Disproportionably long in part.—Ex. Abdomen of
Libellulina.
1. Short (Brevis). Disproportionably short throughout.—Ex. Copris.
2. Abbreviate (Abbreviata). Disproportionably short in part.—Ex. Elytra
of Staphylinidæ, Atractocerus, &c.

V. FIGURE[1079].

. Circular (Circularis). Having the diameter every way equal. Plate
XXIX. Fig. 16, 17.
. Rotundate (Rotundata). Rounded at the angles or sides. Plate XXIX.
Fig. 19.
. Oval (Ovalis). Having the longitudinal diameter twice the length of the
transverse, and the ends circumscribed by equal segments of a circle.
Plate XX. Fig. 6.
. Elliptic (Elliptica). Oval, but having the longitudinal diameter more than
twice the length of the transverse. Plate XX. Fig. 19.
. Oblong (Oblonga). Having the longitudinal diameter more than twice the
length of the transverse, and the ends varying, or rounded. Plate XX.
Fig. 3, 9.
. Ovate (Ovata). Oval, but having the ends circumscribed by unequal
segments of circles. Plate XX. Fig. 12, 13.
. Cordate (Cordata). Heart-shaped. Ovate or subovate and hollowed out at
the base, without posterior angles. Plate IX. Fig. 22.
. Sagittate (Sagittata). Arrow-shaped. Triangular, hollowed out at the base
with posterior angles. Plate XXVII. Fig. 41. w´´´.

. Hastate (Hastata). Halberd-shaped. Triangular, hollowed out at the base
and sides with the posterior angles spreading.—Ex. Horn of the
prothorax of Dynastes hastatus. Postfurca in many Coleoptera. Plate
XXII. Fig. 5. b †.
0. Triangular; Quadrangular; Quinquangular; Sexangular (Triangula;
Quadrangula; Quinquangula; Sexangula). Having three, four, five, or
six angles.
1. Turbinate (Turbinata). Top-shaped, triangular with curved sides. Plate
XXV. Fig. 18.
2. Ensate (Ensata). Gradually tapering till it ends in a point.—Ex.
Ovipositor of Acrida viridissima. Plate XV. Fig. 19.
3. Lanceolate (Lanceolata). Oblong and gradually tapering towards each
extremity.—Ex. The Cerci in Blatta. Plate XV. Fig. 23. Q´´.
4. Sigmoidal (Sigmoidea). S-shaped. Lanceolate and concave on one side
at the base, and on the other at the apex.—Ex. Ovipositor of Cimbex,
Plate XV. Fig. 21. H´´.
5. Cuneate (Cuneata). Wedge-shaped. Having the longitudinal diameter
exceeding the transverse, and narrowing gradually downwards. Plate
X. Fig. 11.
6. Acinacicate (Acinacicata). Falchion-shaped. Curved with the apex
truncate, and growing gradually wider towards the end.—Ex. Abdomen
of Ophion, Fœnus, and other Ichneumonidæ[1080].
7. Lunulate (Lunulata). Crescent-shaped. Curved with both ends acute,
like the moon in her first quarter.—Ex. Last joint of the labial palpi of
Oxyporus. Plate XIII. Fig. 4. a.
8. Falcate (Falcata). Sickle-shaped. Curved with the apex acute.—Ex.
Ovipositor of Acrida varia. Antennæ of Atractocerus. Plate XI. Fig. 8.
9. Linear (Linearis). Narrow and of the same width throughout.—Ex.
Wings of Pterophorus monodactylus.

0. Arcuate (Arcuata). Linear and bent like a bow.—Ex. Rostrum of
Balaninus Nucum. Plate XIII. Fig. 12.
1. Cultrate (Cultrata). Coulter-shaped. Straight on one side and curved on
the other.—Ex. Ovipositor of some Saw-flies. Under-wing of many
Ichneumonidæ.
2. Spatulate (Spatulata). Spatula-shaped. Broader and rounded at the
apex, linear and narrow at the base.—Ex. Abdomen of Ichneumon
amictorius Panz.
3. Clepsydrate (Clepsydrata). Hour-glass-shaped. Broader at the base and
apex—Ex. The Prosternum of many Capricorn beetles.
4. Clavate (Clavata). Club-shaped. Linear at the base, but towards the
apex growing gradually broader. Plate XI. Fig. 4.
5. Quadrate (Quadrata). Square. Quadrilateral with the sides equal and
the angles right angles.
6. Rhomboid (Rhomboidea). Quadrilateral with the sides equal, but with
two opposite angles acute, and two obtuse. Plate XXVII. Fig. 62. t´´.
7. Trapezate (Trapezata). Quadrilateral with the four sides unequal, and
none of them perfectly parallel. Plate XIV. Fig. 4.
8. Trapezoid (Trapezoidea). Quadrilateral, with two sides unequal and
parallel[1081]. Plate XXVI. Fig. 34. b´.
9. Parallelogramical (Parallelogramica). Quadrilateral, with all the
angles right angles, and all the sides parallel, but two longer than the
others.

VI. FORM[1082].

. Spherical (Sphærica). The shape of a globe. A body whose diameter
every way is equal. Plate XX. Fig. 5.
. Orbiculate (Orbiculata). A depressed globe, whose horizontal section is
circular, and vertical oval. Plate XX. Fig. 10, 11.

. Lenticular (Lenticularis). Lens-shaped. Whose horizontal section is
circular, and vertical lanceolate.—Ex. Abdomen of Cynips aptera.
. Ovaliform (Ovaliformis). Whose longitudinal section is oval, and
transverse circular. Plate XX. Fig. 6.
. Ellipsoid (Ellipsoidea). Whose longitudinal section is elliptical, and
transverse circular. Plate XX. Fig. 19.
. Oviform (Oviformis). Whose longitudinal section is ovate, and
transverse circular. Plate XX. Fig. 12, 13.
. Cucumiform (Cucumiformis). Cucumber-shaped. Whose longitudinal
section is oblong, and transverse circular. Plate XX. Fig. 18,
excluding the neck.
. Cordiform (Cordiformis). Oviform and hollowed out at the base without
posterior angles. Plate IX. Fig. 22.
. Conical (Conica). Whose vertical section is triangular, and horizontal
circular.—Ex. Abdomen of Cœlioxys conica (Apis * * b. K.). Plate
XX. Fig. 7.
0. Turbiniform (Turbiniformis). Whose vertical section is turbinate, and
horizontal circular.—Ex. Joints of antennæ of Aleochara socialis, and
many others of that genus.
1. Pyramidal (Pyramidalis). Whose vertical section is triangular, and
horizontal quadrangular.
2. Cuneiform (Cuneiformis). Whose vertical section is cuneate, and
horizontal parallelogramical.
3. Triquetrous (Triquetra). Whose horizontal sections are equilateral
triangles. Plate XI. Fig. 6.
4. Ensiform (Ensiformis). Whose horizontal sections are acute-angled
triangles gradually diminishing in diameter from the base to the apex,
and propagated in a straight line. Plate XI. Fig. 7.

5. Acinaciform (Acinaciformis). Whose horizontal sections are acute-
angled triangles gradually increasing in diameter from the base to the
apex, and propagated in a curved line.
6. Cultriform (Cultriformis). Whose horizontal sections are equal acute-
angled triangles, or a three-sided body with two equal sides large and
the third small.
7. Deltoid (Deltoidea). Short with the horizontal section triangular and
decreasing in diameter towards the base.—Ex. Apex of the posterior
tibia in Copris lunaris.
8. Trigonal; Tetragonal; Pentagonal; Hexagonal; Polygonal (Trigona;
Tetragona; Pentagona; Hexagona; Polygona). Whose horizontal
section is triangular; quadrangular; quinquangular; sexangular;
multiangular.
9. Triedral; Tetraedral; Pentaedral; Hexaedral; Polyedral (Triedra;
Tetraedra; Pentaedra; Hexaedra; Polyedra). That hath three sides;
four sides; five sides; six sides; many sides.
0. Prismoidal (Prismoidalis). Having more than four sides and whose
horizontal section is a polygon[1083]. Plate VI. Fig. 13. a, b, d´.
1. Trapeziform (Trapeziformis). Whose horizontal section is a Trapezium.
2. Trapezoidiform (Trapezoidiformis). Whose horizontal section is
trapezoid.
3. Rhombiform (Rhombiformis). Whose horizontal section is rhomboidal.
Plate VIII. Fig. 11.
4. Two-edged (Anceps). Whose horizontal section is lanceolate.
5. Cylindrical (Cylindrica). Whose horizontal sections are all equal
circles. Plate XXI. Fig. 4.
6. Fusiform (Fusiformis). Spindle-shaped. Whose vertical section is
lanceolate or lineari-lanceolate, and horizontal circular. Plate XXIII.
Fig. 12.

7. Columnar (Teres). Whose vertical section is cuneate, and horizontal
circular. Plate XVI. Fig. 2, 3.
8. Claviform (Claviformis). Whose vertical section is clavate, and
horizontal circular. Plate XI. XII. Fig. 4.
9. Cubical (Cubica). Six-sided, with sides quadrate.
0. Parallelopipedous (Parallelopipeda). Six-sided, with four
parallelogramical and two quadrate sides.
1. Pyriform (Pyriformis). Pear-shaped. Whose vertical section is spatulate,
and horizontal circular.—Ex. Apion, &c.
2. Infundibuliform (Infundibuliformis). Funnel-shaped. Whose horizontal
sections are circular, at first equal and then progressively larger and
larger. Plate XXII. Fig. 12. c.
3. Fornicate (Fornicata). Convex above and concave beneath. Plate XIII.
Fig. 18. a.
4. Coarctate (Coarctata). When the diameter of the middle is less than
that of the ends.—Ex. Posterior thigh of Locusta. Plate XIV. Fig. 5.
5. Calceoliform (Calceoliformis). Oblong, and somewhat coarctate in the
middle.—Ex. Abdomen of Chelonus.
6. Lageniform (Lageniformis). Bellying out and then ending in a narrow
neck, something like a bottle.—Ex. Sperm-reservoir attached to the
oviduct in Pontia. Plate XXX. Fig. 12. d.
7. Constrict (Constricta). Suddenly and disproportionably smaller at one
end. Plate XXII. Fig. 15.
8. Luniform (Luniformis). Whose longitudinal section is lunate. Plate
XIII. Fig. 4.
9. Nodose (Nodosa). Having one or more knobs or swellings. Plate XII.
Fig. 5.
0. Geniculate (Geniculata). Bent so as to form a knee or angle. Plate XII.
Fig. 7.

VII. SUPERFICIES.
i. PARTS.

. Disk (Discus). The middle of a surface.
. Limb (Limbus). The circumference.
. Margin (Margo). The extreme sides.
. Apex (Apex). The summit.
. Base (Basis). The bottom.
. Supine Surface (Pagina superior). The upper surface.
. Prone Surface (Pagina inferior). The under surface.

ii. ELEVATION and DEPRESSION.

. Navicular (Navicularis). When two sides meet and form an angle like
the outer bottom of a boat.—Ex. Notonecta glauca.
. Convex (Convexa). An elevation the arc of which is the segment of a
circle.—Ex. Upper Surface of the body of most Coleoptera.
. Gibbous (Gibba). An elevation the arc of which is not the segment of a
circle[1084].—Ex. Shoulders of the elytra of Prionus coriarius, and of
many other Coleoptera.
. Plane (Plana). Flat. When the disk is not higher than the limb, nor the
limb than the disk.
. Concave (Concava). A depression the arc of which is the segment of a
circle.
. Excavate (Excavata). A depression the arc of which is not the segment of
a circle.—Ex. Prothorax of Sinodendrum cylindricum.

iii. SCULPTURE.

. Equate[1085] (Æquata). Without larger partial elevations or depressions.

. Smooth (Lævis). Without smaller partial elevations or depressions.
. Levigate (Lævigata). Without any partial elevations or depressions.
. Pore (Porus). A minute impression that perforates the substance.
. Porose (Porosa). Beset with many pores.—Ex. Elytra of most Apions.
. A Point (Punctum). A minute impression upon the surface, but not
perforating it.
. Punctate (Punctata). Beset with many points.—Ex. Impression on the
Head and Prothorax of Phyllopertha Horticola, &c.
. Variole (Variola). A shallow impression like a mark of the small-pox.
. Variolous (Variolosa). Beset with many varioles.—Ex. Scarabæus
variolosus.
0. Umbilicate (Umbilicata). When a variole, tubercle, granule, &c. has a
depression in its centre.—Ex. Thorax of Pachygaster scabrosus.
1. Foveolet (Foveola). A roundish and rather deep depression, larger than
a variole.
2. Foveolate (Foveolata). Having one or more foveolets.—Ex. Prothorax
of Geotrupes stercorarius.
3. Fossulet (Fossula). A somewhat long and narrow depression.
4. Fossulate (Fossulata). Having one or more fossulets.—Ex. Oxytelus
rugosus, &c.
5. Unequal (Inæqualis). Having very slight and indeterminate
excavations.—Ex. Prothorax of Silpha thoracica, Cerambyx
moschatus, &c.
6. Lacunose (Lacunosa). Having a few scattered, irregular, broadish but
shallow excavations.—Ex. Elytra of Donacia vittata, Sagittariæ, &c.
7. Rimose (Rimosa). Chinky, resembling the bark of a tree. Having
numerous minute, narrow and nearly parallel excavations, which run

into each other.—Ex. Elytra of Colymbetes adspersus ♀, and Cybister
Rœselii.
8. Undose (Undosa). Having undulating nearly parallel broader
depressions which run into each other, and resemble the sand of the
sea-shore when left by the tide.—Ex. Cymatodes[1086] undosus K. MS.
9. Vermiculate (Vermiculata). Having tortuous excavations as if eaten by
worms.—Ex. Prothorax of Colymbetes Hybneri and transversalis.
0. Reticulose (Reticulosa). Having a number of minute impressed lines
which intersect each other in various directions like the meshes of a
net.—Ex. Prothorax of Cybister Rœselii.
1. Acuducted (Acuducta). Scratched across very finely as if with the point
of a needle or pin.—Ex. Colymbetes acuductus.
2. Striate (Striata). Having rather slightly impressed longitudinal parallel
lines.—Ex. Amara communis, &c.
3. Sulcate (Sulcata). Having deeper impressed longitudinal parallel lines.
—Ex. Dytiscus marginalis ♀.
4. Clathrose (Clathrosa). When strias or furrows cross each other at right
angles.—Ex. Abdomen of Micropeplus porcatus.
5. Rivose (Rivosa). When furrows do not run in a parallel direction and are
rather sinuate.—Ex. Prothorax of Elophorus stagnalis, &c.
6. Interstice (Interstitium). The space between elevations and depressions
running in lines.
7. Interval (Intervallum). The space between irregular and scattered
elevations and depressions.
8. Complanate (Complanata). A convex or irregular surface having a plane
slight depression.—Ex. Sides of the Prothorax of Prionus cervicornis.
9. Canaliculate (Canaliculata). Having a longitudinal impressed line or
channel.—Ex. Prothorax of Geotrupes, Broscus cephalotes, &c.

0. Carinate (Carinata). Having a longitudinal elevated line.—Ex. Rostrum
of Curculio nebulosus. Bicarinate, Tricarinate, &c., having two or
three such lines.—Ex. Elytra of Silpha recta.
1. Cristate (Cristata). Having one or two very elevated lines usually
crenate.—Ex. Prothorax of Pterophylla laurifolia.
2. Porcate (Porcata). Having several parallel elevated longitudinal ridges.
—Ex. Onthophilus striatus.
3. Costate (Costata). Having several broad elevated lines.—Ex. Brachinus
bimaculatus, &c.
4. Clathrate (Clathrata). Having several elevated lines which cross each
other at right angles.—Ex. Abdomen of Micropeplus porcatus.
5. Reticulate (Reticulata). Having many small elevated lines which
intersect each other in various directions like the meshes of a net.—Ex.
Lycus reticulatus. Wings of the Libellulina.
6. Rugose (Rugosa). Wrinkled. Intricate with approximating elevations
and depressions whose direction is indeterminate.—Ex. Elytra of
Prionus coriarius.
7. Cicatricose (Cicatricosa). Having elevated spots of a different colour
from the rest of the surface, resembling scars.—Ex. Elytra of
Ptomaphila lachrymosa K. MS[1087].
8. Embossed (Cælata). Having several plane tracts of a different shape
higher than the rest of the surface.—Ex. Prothorax of Prionus
damicornis, maxillosus, &c.
9. Gibbose (Gibbosa). Having one or more large elevations.—Ex. Sides of
the Prothorax of Brachycerus barbarus.
0. Tubercle (Tuberculum). A pimple-like knob.
1. Tuberculate (Tuberculata). Having several tubercles.—Ex. Apoderus
gemmatus. Base of Prothorax of Cerambyx moschatus.
2. Verruca. A small flattish wart-like prominence.

3. Verrucose (Verrucosa). Having several verrucæ.—Ex. Pimelia
muricata.
4. Muricate (Muricata). Armed with sharp thick, but not close, elevated
points like a Murex.—Ex. Bronchus Tribulus, quadridens[1088], &c.
5. Echinate (Echinata). Armed with sharp spines like a hedgehog or
Echinus.—Ex. Hispa atra.
6. Rugged (Salebrosa). When a surface is rough with mucros, spines and
tubercles intermixed.—Ex. Numerous species of Bronchus.
7. Granule (Granulum). A very minute elevation.
8. Granulate (Granulata). Beset with many granules like shagreen.—Ex.
Otiorhynchus sulcatus. Prothorax of Copris Molossus.
9. Scabrous (Scabra). Rough to the touch from granules scarcely visible.
—Ex. Elytra of Otiorhynchus Ligustici.
0. Papillule (Papillula). A tubercle or variole with an elevation in its
centre.
1. Papillulate (Papillulata). Beset with many papillules.—Ex. Elytra of
Dynastes Hercules ♀.
2. Catenulate (Catenulata). Having a series of elevated oblong tubercles
resembling a chain.—Ex. Carabus catenulatus.
3. Spherulate (Sphærulata). Having one or more rows of minute tubercles.
—Ex. Trox lutosus, Limnius tuberculatus.
4. Consute (Consuta). Having very minute elevations in a series at some
distance from each other, of a different colour from the rest of the
surface, and somewhat resembling stitching.—Ex. Elytra of Oryctes
Sylvanus (Cœlosis K. MS.).
5. Intricate (Intricata). When depressions or elevations so run into each
other as to be difficult to trace.—Ex. Elytra of Carabus intricatus.

6. Corrugate (Corrugata). When a surface rises and falls in parallel
angles more or less acute.—Ex. Front of Nothiophilus aquaticus.
7. Obliterate (Obliterata). Applied to impressions and elevations when
almost effaced.

iv. CLOTHING.
a. general.

. Scutate (Scutata). Covered with large flat scales.—Ex. Machilis
polypoda.
. Squamose (Squamosa). Covered with minute scales.—Ex. Lepidoptera.
. Pulverulent (Pulverulenta). Covered with very minute powder-like
scales.—Ex. Ceutorhynchus Sisymbrii.
. Pollinose (Pollinosa). Covered with a loose mealy and often yellow
powder resembling the pollen of flowers.—Ex. Lixus paraplecticus.
. Farinose (Farinosa). Covered with a fixed mealy powder resembling
flour.—Ex. Spots on the Elytra of Cetonia aurata, variegata, &c.
. Lutose (Lutosa). Covered with a powdery substance resembling mud or
dirt, which easily rubs off.—Ex. Trox lutosus.
. Rorulent (Rorulenta). Covered like a plum with a bloom which may be
rubbed off.—Ex. Peltis limbata.
. Stupeous (Stupea). Covered with long loose scales resembling tow.—Ex.
The Palpi of Lepidoptera. Antennæ of some Diptera. Plate XII. Fig.
23.
. Pilose (Pilosa). Covered with long distinct flexible hairs.—Ex. Thorax of
Vespa Crabro.
0. Villose (Villosa). Covered with soft flexible hairs thickly set.—Ex.
Prothorax of Amphimalla solstitialis.
1. Lanate (Lanata). Covered with fine, very long, flexible and rather
curling hairs like wool.—Ex. Melolontha lanigera F.

2. Lanuginose (Lanuginosa). Covered with longish very soft fine down.—
Ex. Prothorax of Trichius fasciatus. Thorax and base of the Abdomen
of Megachile circumcincta (Apis **. c. 2. α K.).
3. Hirsute (Hirsuta). Covered with long stiffish hairs very thickly set.—
Ex. Bombus.
4. Plumulose (Plumulosa). When the hairs branch out laterally like
feathers.—Ex. Hair on the base of the Maxilla of Eucera (Apis ** d. 1.
K.).
5. Hairy (Hirta). Covered with short stiffish sub-distinct hairs.—Ex.
Genus Lagria.
6. Tomentose (Tomentosa). Covered with short interwoven inconspicuous
hairs.—Ex. Acanthocinus Ædilis.
7. Pubescent (Pubescens). Covered with very fine decumbent short hairs.
—Ex. Harpalus ruficornis, &c.
8. Stupulose (Stupulosa). Covered with coarse decumbent hairs.—Ex.
Elytra of Melolontha vulgaris.
9. Velutinous (Velutina). Covered with very thick-set upright short hairs
or pile, resembling velvet.—Ex. Trombidium holosericeum. Scutellum
of Staphylinus hybridus.
0. Holosericeous (Holosericea). Covered with thick-set shining short
decumbent hairs, resembling satin[1089].—Ex. Under side of the body
of Elophorus stagnalis, Argyroneta aquatica, &c.
1. Setose (Setosa). Bristly. Sprinkled with stiff scattered hairs like bristles.
—Ex. Echinomyia grossa.
2. Setulose (Setulosa). Setose with the bristles truncated.—Ex. Thylacites
setosus.
3. Hispid (Hispida). Rough from minute spines, or very stiff rigid bristles.
—Ex. Hispa atra. Phoberus horridus, &c.
4. Rough (Aspera). Rough from pubescence in general.

5. Bald (Calva). A part of a surface with little or no hair, when the rest of
it is very hairy.—Ex. Vertex of Melitta and Apis Kirby.
6. Glabrous (Glabra). Without any hair or pubescence.
7. Lubricous (Lubrica). Slippery as if lubricated.—Ex. Dynastes
Centaurus.

b. partial.

. Cirrus (Cirrus). A lock of curling hair.
. Cirrose (Cirrosa). Having one or more cirri.—Ex. Antennæ of
Acanthocinus araneiformis.
. Fascicule (Fasciculus). A bundle of thick-set hairs often converging at
the apex. Plate XIX. Fig. 6. c.
. Fasciculate (Fasciculata). Having one or more fascicules.—Ex.
Catenulated lines in the Elytra of Trox arenosus. Buprestis fascicularis.
. Penicil (Penicillus). A small bundle of diverging hairs. Plate XIX. Fig. 6.
a.
. Penicillate (Penicillata). Having one or more penicils.—Ex. Larva of
Orgyia antiqua.
. Verricule (Verriculum). A thick-set tuft of parallel hairs. Plate XIX. Fig.
6. b.
. Verriculate (Verriculata). Having one or more verricules.—Ex. Larva of
Dasychira pudibunda. Under side of Abdomen of Megachile ♀. (Apis
**. c. 2. α. K.).
. Barbate (Barbata). When any part is clothed with longer hairs,
resembling a beard.—Ex. Anus of Macroglossa stellatarum. Antennæ
of Cerambyx Ammiralis L. Plate XII. Fig. 26.
0. Ciliate (Ciliata). When the margin is fringed with a row of parallel
hairs.—Ex. The base and apex of the Prothorax of Lucanus Cervus.

1. Fimbriate (Fimbriata). When a part is terminated by hairs or bristles that
are not parallel.—Ex. Anus of many Andrenæ[1090]. (Melitta **. c. K.).
2. Comate (Comata). When very long flexible hairs thickly cover a space
in the upper surface.
3. Crinite (Crinita). When very long hairs thinly cover any space.
4. Jubate (Jubata). Having long pendent hairs in a continued series.—Ex.
Intermediate Legs of Anthophora pilipes (Apis **. d. 2. α. K.).
5. Furred (Pellita). When shorter decumbent hairs thickly cover any
space, as in the Bombyces dorso cristato L.

v. COLOUR.

. Niveous (Niveus). The pure unblended white of snow.—Ex. Arctia
chrysorhea.
. White (Albus). White less intense than niveous. The colour of chalk.—
Ex. Spilosoma mendica ♀.
. Lacteous (Lacteus). White with a slight tint of blue. The colour of milk.
—Ex. Minoa lactearia.
. Cream-coloured (Lactifloreus). White with a proportion of yellow.—Ex.
Pale part of the Primary wings of Euprepia Caja.
. Flesh-coloured (Carneus). White tinted with red. The colour of young
and healthy flesh.—Ex. Secondary wings of Sphinx Ligustri.
. Hoary (Incanus). White with a small proportion of black. The colour of a
gray head. N.B. This term is usually confined to pubescence.—Ex.
Curculio sulcirostris.
. Cinereous (Cinereus). White with a shade of brown.—Ex. Sitona diffinis,
Dasychira pudibunda.
. Griseous (Griseus). White mottled with black or brown.—Ex. Curculio
nebulosus.

. Yellow (Flavus). Pure yellow.—Ex. Bands on the Abdomen of Nomada
(Apis *. b. K.), Crabro, &c.
0. Straw-coloured (Stramineus). Pale yellow with a very faint tint of blue.
—Ex. Ennomos cratægata.
1. Sulphureous (Sulphureus). Yellow with a tint of green. The colour of
brimstone.—Ex. Gonepteryx Rhamni ♂.
2. Luteous (Luteus). Deep yellow with a tint of red. The colour of the yolk
of an egg.—Ex. Primary wings of Colias Edusa.
3. Orange (Aurantius). Equal parts of red and yellow.—Ex. Apex of Wings
of Pontia Cardamines.
4. Saffron-coloured (Croceus). The colour of saffron.—Ex. Yellow in the
Elytra of Trichius fasciatus.
5. Miniatous (Miniatus). The colour of red lead.—Ex. Secondary wings of
Euprepia Caja.
6. Fulgid (Fulgidus). A bright fiery red.—Ex. Lycæna Virgaureæ and
Hippothoe.
7. Rufous (Rufus). A pale red.—Ex. Apion frumentarium.
8. Testaceous (Testaceus). The colour of a tile, a dull red.—Ex.
Chrysomela Populi.
9. Scarlet (Coccineus). A bright pale red.—Ex. Elytra of Pyrochroa
coccinea.
0. Red (Ruber). Pure red.—Ex. Under Wings of Hypercampa Dominula.
1. Sanguineous (Sanguineus). Red with a tint of black. The colour of
blood.—Ex. Spots in Chilocorus Cacti, and Prothorax of Locusta
morbillosa.
2. Rose-coloured (Roseus). Colour of the rose.—Ex. Parts of the Wings
and Body of Deilephila Elpenor.

3. Crimson (Puniceus). A bright red with a tint of blue.—Ex. Base of the
Under Wings of Catocala Sponsa.
4. Purple (Purpureus). Equal parts of blue and red.—Ex. Sagra purpurea.
Vitta on the Elytra of Donacia fasciata.
5. Violet (Violaceus). Blue with some red. The colour of Viola odorata.—
Ex. Chrysomela Goettingensis, Abdomen of Geotrupes vernalis.
6. Lilac (Lilacinus). Colour of the flowers of the lilac.—Ex. Part of the
Iris of the Ocellus, in the Wings of Vanessa Io.
7. Blue (Cyaneus). Pure blue. Colour of Centaurea Cyanus.—Ex. Disk of
the Wings of Papilio Ulysses. Callidium violaceum.
8. Azure (Azureus). A paler and more brilliant blue.—Ex. Wings of
Morpho Menelaus, Telemachus, &c.
9. Sky-Blue (Cæruleus). A paler blue. The colour of the sky.—Ex.
Polyommatus Adonis.
0. Cæsious (Cæsius). Very pale blue with a little black. The colour of blue
eyes.—Ex. Under side of the Wings of Polyommatus Argiolus.
1. Green (Viridis). Equal parts of blue and yellow.—Ex. Cicindela
campestris.
2. Æruginous (Æruginosus). Green with a blue tint. The colour of the rust
of copper, verdigris.—Ex. Polydrosus Cnides.
3. Prasinous (Prasinus). Green with a mixture of yellow. The colour of the
leaves of leeks or onions.—Ex. Pentatoma prasina. Under side of
Wings of Thecla Rubi.
4. Glaucous (Glaucus). Pale blueish green. Sea green.—Ex. Elytra of
Dynastes Hercules, Alcides, Tityus, &c.
5. Mouse-coloured (Murinus). Black with a small proportion of yellow.
The colour of the common mouse.—Ex. Base of the abdominal
segments of Cossus ligniperda.

6. Lurid (Luridus). Yellow with some mixture of brown. Dirty yellow.—
Ex. Elytra of Aphodius luridus and nigrosulcatus.
7. Livid (Lividus). A pale purplish brown. The colour of a bruise.—Ex.
Berosus luridus.
8. Tawny (Fulvus). A pale dirty orange.—Ex. The pale parts of the Wings
of Hipparchia Pamphilus.
9. Fawn-coloured (Cervinus). A reddish brown.—Ex. Lasiocampa Rubi.
0. Olive (Olivaceus). A brownish green. The colour of olives.—Ex.
Dytiscus marginalis.
1. Fuscous (Fuscus). A dull brown.—Ex. Hipparchia Semele. Prionus
scabricornis.
2. Ferruginous (Ferrugineus). A yellowish brown with some red. The
colour of the rust of iron.—Ex. Base of Under Wings of Smerinthus
Populi. Gastropacha quercifolia.
3. Cinnamon-coloured (Cinnamomeus). A yellowish brown. The colour of
cinnamon.—Ex. Prionus cinnamomeus.
4. Brown (Brunneus). Pure brown.—Ex. Dark parts in the Primary Wings
of Euprepia Caja.
5. Bay (Badius). Bright red brown of the chestnut.—Ex. Elytra of
Melolontha vulgaris when the hairs are rubbed off.
6. Chestnut (Castaneus). Colour of the dark part of the chestnut.—Ex.
Elytra of Lucanus Cervus.
7. Piceous (Piceus). Shining reddish black. The colour of pitch.—Ex.
Prionus coriarius.
8. Fuliginous (Fuliginosus). The opaque black of soot.—Ex. Wings of
Lithosia rubricollis.
9. Black (Niger). A dull black with some brown.—Ex. Pachygaster niger.
0. Atrous (Ater). Pure black of the deepest tint.—Ex. Liparus anglicanus.

vi. SPLENDOUR.
a. gemmeous.

. Margaritaceous (Margaritaceus). Glossy, white with changeable tints of
purple, green, and blue. The splendour of pearls.—Ex. The drums in
Cicada capensis.
. Opaline (Opalinus). A blueish white reflecting the prismatic colours. The
splendour of the opal.—Ex. Wings of Notonecta glauca and some
Nepæ.
. Crystalline (Crystallinus). The white splendour of crystal or glass.—Ex.
Stemmata of many Hymenoptera, &c.
. Topazine (Topazinus). The yellow splendour of the topaz.—Ex. Many
Stemmata of Hymenoptera, and Eyes of Spiders.
. Rubineous (Rubineus). The red splendour of the ruby.
. Smaragdine (Smaragdinus). The green splendour of the emerald.
. Amethystine (Amethystinus). The purple splendour of the amethyst.

b. metallic.

. Argent (Argenteus). The splendour of silver.—Ex. The spots on the
under side of the Wings in Argynnis Lathonia, &c.
. Golden (Aureus). The splendour of gold.—Ex. Entimus imperialis. Spot
in the Wings of Plusia Festucæ.
. Orichalceous (Orichalceus). A splendour intermediate between that of
gold and brass.—Ex. Upper Wings of Plusia Chrysitis.
. Æneous (Æneus). The splendour of brass.—Ex. Elytra of Carabus
clathratus.
. Cupreous (Cupreus). The reddening splendour of copper.—Ex. Carabus
nitens.

. Chalybeous (Chalybeus). The blue splendour of steel case-hardened, or
of the mainspring of a watch.—Ex. Helops chalybeus. Legs of Lithosia
Quadra.
. Plumbeous (Plumbeus). The colour of lead.—Ex. Prothorax of Clytra
dentata?
. Inaurate (Inauratus). When striæ or other impressed parts have a
metallic splendour.—Ex. Margin of Prothorax and Elytra of Carabus
violaceus. Striæ of Elytra &c. of Phanæus Mimas.
. Deaurate (Deauratus). A metallic hue which looks as if the gilding was
worn off.—Ex. Donacia ænea, &c.

c. bombycine.

. Sericeous (Sericeus). The splendour of silk.—Ex. Cryptocephalus
sericeus.
. Tramosericeous (Tramosericeus). The splendour of satin.—Ex. Chlamys
Bacca, monstrosa, &c.

d. reflected.

. Resplendent (Splendens). Reflecting the light intensely.—Ex. The Head
and Thorax of Philonthus splendens, æneus, politus, &c.
. Shining (Nitidus). Reflecting the light, but less intensely.—Ex. Dytiscus
marginalis.
. Pruinose (Pruinosus). When the splendour of the surface is somewhat
obscured by the appearance of a bloom upon it like that of a plum, but
which cannot be rubbed off[1091].—Ex. Elytra of Serica ruricola and
brunnea.
. Obscure (Obscurus). A surface which reflects the light but little.—Ex.
Pælobius Hermanni.
, Opaque (Opacus). A surface which does not reflect the light at all.—Ex.
Trox sabulosus, arenarius. Silpha opaca.

vii. TRANSPARENCE.

. Hyaline (Hyalina). The clear transparency of glass.—Ex. The Wings of
many Neuroptera, Hymenoptera, and Diptera.
. Diaphanous (Diaphana). Transparent, but less purely than hyaline.
Semitransparent.—Ex. The Wings of many Coleoptera.
. Adiaphanous (Adiaphana). Which does not transmit the light at all.—Ex.
Elytra of Coleoptera.

viii. PAINTING.

. Atom (Atomus). A very minute dot.
. Irrorate (Irrorata). Sprinkled with atoms, as the earth with dew.—Ex.
Onthophagus Vacca. Papilio Paris.

. Gutta (Gutta[1092]). A roundish dot intermediate in size between an atom
and a macula.
. Guttate (Guttata). Sprinkled with guttæ.—Ex. Coccinella.
. Macula (Macula). A larger indeterminately shaped spot.
. Maculate (Maculata). Painted with such spots.—Ex. Abraxas
grossulariata.
. Litura (Litura). An indeterminate spot growing paler at one end, as if
daubed or blotted.
. Liturate (Liturata). A surface painted with one or more such spots.—Ex.
Aphodius conflagratus.
. Plaga (Plaga). A long and large spot.—Ex. Aphodius plagiatus.
0. Islet (Insula). A spot of a different colour, included in a plaga or
macula.—Ex. The Ocelli in the Primary Wings of Hipparchia Semele.
A spot in the middle fascia of the under side of the Primary Wing in
Papilio Podalirius.

1. Crepera (Crepera). A gleam of paler colour upon a dark ground.—Ex.
Elytra of Dytiscus marginalis.
2. Shadow (Umbra). A slight shade, not easily perceptible upon a paler
ground.—Ex. Elytra of Acanthocinus Ædilis. Wings of Plutella
asperella.
3. Signatures (Signaturæ). Markings upon a surface resembling in some
degree letters and characters.
4. Signate (Signatus). Marked with signatures.—Ex. Elytra of Acrocinus
longimanus.
5. Inscribed (Inscriptus). When the surface is marked with the
resemblance of a letter of any language.—Ex. Plusia Gamma. Vanessa
C. album.
6. Hieroglyphic (Hieroglyphicus). Painted with characters somewhat
resembling hieroglyphics.—Ex. Acrocinus longimanus. Schizorhina
Australasiæ.
7. Annulet (Annulus). A ring-shaped spot.—Ex. Cyclophora omicronaria,
&c. Plate XIV. Fig. 1. o.
8. Lunulet (Lunula). A small crescent-shaped spot.—Ex. Marginal spots
above and below the Secondary Wings in Melitæa Artemis, &c.
9. Reniculus (Reniculus). A small kidney-shaped spot.—Ex. Upper Wings
of Mamestra Persicaria.
0. Ocellus (Ocellus). An eye-like spot in the Wings of many Lepidoptera,
consisting of annuli of different colours, inclosing a central spot or
pupil.
Pupil (Pupilla). The central spot of the ocellus. Plate XIV. Fig. 1. t. An
ocellus is called bipupillate, tripupillate, &c., when there are two,
three, &c. of these spots.—Ex. Primary Wing of Hipparchia Tithonus,
&c. Plate XIV. Fig. 1. p.
Hastate Pupil (Pupilla hastata). When the pupil is a halberd-shaped spot.
—Ex. Pupil of Ocellus of Aglia Tau. Plate XIV. Fig. 1. k.

Suffulted Pupil (Pupilla suffulta). When the pupil shades into another
colour.—Ex. Primary Wing of Vanessa Io.
. Iris (Iris). The circle which incloses the pupil. Plate XIV. Fig. 1. u.
Atmosphere (Atmosphæra). The exterior circle of the ocellus. Plate XIV.
Fig. 1. v.
1. Blind Ocellus (Ocellus cæcus). An ocellus without the pupil.—Ex.
Hipparchia Davus.
2. Spurious Ocellus (Ocellus spurius). A circular spot without any defined
iris or pupil.—Ex. Spot in the Disk of the Primary Wings of Colias
Helice.
3. Simple Ocellus (Ocellus simplex). When the ocellus consists only of iris
and pupil.—Ex. Ocelli on the under side of Primary Wings of
Hipparchia Semele. Plate XIV. Fig. 1. t, n, u.
4. Compound Ocellus (Ocellus complexus). When the ocellus consists of
three or more circles.—Ex. Saturnia Spini. Plate XIV. Fig. 1. l.
5. Nictitant Ocellus (Ocellus nictitans). When the ocellus includes a
lunular spot of a different colour.—Ex. Under side of Wings of
Morpho Perseus. Plate XIV. Fig. 1. m.
6. Fenestrate Ocellus (Ocellus fenestratus). When an ocellus has a
transparent spot.—Ex. Attacus Paphia and Cytherea.
7. Dioptrate Ocellus (Ocellus dioptratus). A fenestrate ocellus divided by
a transverse line.—Ex. Attacus Polyphemus.
8. Double Ocellus (Ocellus geminatus). When two ocelli are included in
the same circle or spot.—Ex. Under side of Secondary Wing of
Morpho Perseus. Plate XIV. Fig. 1. r, v.
9. Twin Ocellus (Ocellus didymus). When such ocelli join each other.—
Ex. Under side of Secondary Wing of Hipparchia Hyperanthus.
0. Sesquialterous Ocellus (Ocellus sesquialterus). An ocellus with a
smaller near it, called also Sesquiocellus.—Ex. Under side of

Secondary Wing of Colias Edusa. Plate XIV. Fig. 1. q.
1. Supercilium (Supercilium). An arched line resembling an eyebrow,
which sometimes surmounts an eyelet.—Ex. Under side of Secondary
Wing of Morpho Achilles. Plate XIV. Fig. 1. i.
2. Nebulose (Nebulosus). Painted with colour irregularly darker and
lighter, so as to exhibit some resemblance of clouds.—Ex. Curculio
sulcirostris, nebulosus; Catocala nupta.
3. Testudinarious (Testudinarius). Painted with red, black and yellow, like
tortoise-shell.—Ex. Elytra of Aphodius testudinarius.
4. Consperse (Conspersus). Thickly sprinkled with minute irregular dots
often confluent.—Ex. Biston Betularia.
5. Achatine (Achatinus). Painted with various concentric, curved, or
parallel lines, resembling the veining of an agate.—Ex. Cossus
labyrinthicus. Cerura vinula.
6. Ustulate (Ustulata). So marked with brown as to have the appearance
of being scorched.—Ex. Wings of Ennomos dolabraria.
7. Marmorate (Marmorata). So painted with streaks, veins, and clouds, as
to resemble marble.—Ex. Under side of the Wings of Vanessa Io.
Marmarina marmorata.
8. Tessellate (Tessellata). Painted in checquerwork.—Ex. Abdomen of
Sarcophaga carnaria and Musca maculata.
9. Fascia (Fascia). A broad transverse band.
Pyramidate Fascia (Fascia pyramidata). A band which juts out into an
angle on one side.—Ex. Wing of Apatura Iris. Argynnis Paphia. Plate
XIV. Fig. 1. h.
. Macular Fascia (Fascia macularis). A band consisting of distinct spots.
—Ex. Wings of Abraxas grossulariata. Plate XIV. Fig. 1. b.
Articulate Fascia (Fascia articulata). A band consisting of contiguous
spots.—Ex. Under side of Wings of Melitæa Dictynna. Upper side of

Primary Wing of Morpho Menelaus. Plate XIV. Fig. 1. a.
. Dimidiate Fascia (Fascia dimidiata). A band traversing only half the
wing.—Ex. Primary Wing of Papilio Turnus. Plate XIV. Fig. 1. f.
Abbreviate Fascia (Fascia abbreviata). A band traversing less than half
the wing.—Ex. Primary Wing of Papilio Podalirius, Ajax, &c. Plate
XIV. Fig. 1. g.
Sesquialterous Fascia (Fascia sesquialtera). When both wings are
traversed by a continued band, and either the primary or secondary by
another.—Ex. Endromis versicolor. Plate XIV. Fig. 1. d, c.
. Sesquitertious Fascia (Fascia sesquitertia). When both wings are
traversed by a continued band, and more than half of either the primary
or secondary by another; or, when a wing or elytrum contains a band
and the third of a band.—Ex. Tortrix Avellana. Plate XIV. Fig. 1. d, e.
0. Striga (Striga). A narrow transverse streak.
1. Strigose (Strigosa). Painted with several such streaks.—Ex. Ennomos
prunaria.
2. Line (Linea). A narrow longitudinal stripe.
3. Lineate (Lineata). Painted with several such stripes. N.B. If with two,
we say bilineata, with three, trilineata, &c.—Ex. Elater lineatus.
4. Vitta (Vitta). A broad longitudinal stripe.
5. Vittate (Vittata). Painted with several such stripes.—Ex. Chrysomela
fastuosa, cerealis, &c.
6. Undulate (Undulata). When fasciæ, strigæ, lines, &c. curve into
alternate sinuses resembling the rise and fall of waves.
7. Sinuato-Undulate (Sinuato-Undulata). When the sinuses are obtuse.—
Ex. Boarmia repandaria.
8. Anguloso-Undulate (Anguloso-Undulata). When they go in a zigzag
direction, or with alternate acute sinuses.—Ex. Acidalia undulata.

9. Radiate (Radiata). When a dot, spot, &c. appear to send forth rays.—
Ex. The large blue area common to all the Wings of Papilio Ulysses.
0. Venose (Venosa). Painted with lines that branch like veins.—Ex. Under
side of Wings of Pontia Napi.
1. Cancellate (Cancellata). Painted with transverse lines crossing
longitudinal ones at right angles.—Ex. Macaria clathrata.
2. Areolate (Areolata). Painted with lines which intersect each other in
various directions, so as to exhibit the appearance of net-work.—Ex.
Wings of Tetanocera marginata and Cossus ligniperda.
3. Limbate (Limbata). When the disk is surrounded by a margin of a
different colour.—Ex. Dytiscus marginalis.
4. Armillate (Armillata). When a leg, antenna, &c. is surrounded by a
broad ring of a different colour.—Ex. Posterior Tibia of Prosopis
annulata (Melitta * b. K.).
5. Annulate (Annulata). When a leg, antenna, &c. is surrounded by a
narrow ring of a different colour.—Ex. Antennæ of many Ichneumons.
6. Cingulate (Cingulata). When the abdomen or the trunk is wholly
surrounded by one or more belts of a different colour.—Ex. Abdomen
of many Nomadæ (Apis *. b. K.).
7. Decolorate (Decolor). When the colour appears to be discharged from
any part.—Ex. Margin of the Abdominal segments in Stelis
punctulatissima Latr. (Apis ** c. 1. β. K.).
8. Unicolorate (Unicolor). When a surface is of one colour.
9. Concolorate (Concolor). Of the same colour with another part. If
speaking of Lepidoptera, when the upper and under sides of the wings
are of the same colour.—Ex. Hesperia Linea, Paniscus.
0. Discolorate (Discolor). Of a different colour from another part. When
the upper and under sides of the wings of Lepidoptera are of a
different colour.—Ex. Polyommatus Corydon, Argiolus, &c.

1. Versicolorate (Versicolor). When a surface changes its colour as the
light varies.—Ex. Apatura Iris ♂.
2. Iridescent (Iricolor). When a surface reflects the colours of the
rainbow.—Ex. Mesothorax of Xylocopa iricolor. Wings of
Hymenoptera, &c.
3. Infuscate (Infuscata). When a colour is darkened by the superinduction
of a brownish shade or cloud.—Ex. Apex of the Upper Wings of
Cossus ligniperda.

ix. DISTINCTION.

. Distinct (Distincta). When spots, puncta, granules, &c. do not touch or
run into each other, but are completely separate.—Ex. Under side of
Wings of Lycæna Hippothoe.
. Ordinate (Ordinata). When spots, puncta, &c. are placed in rows. Thus
we say ordinato-punctate, ordinato-maculate, &c.—Ex. Spots on the
Abdomen of Spilosoma lubricipeda, erminea, &c.
. Contiguous (Contigua). When spots, &c. are so near that they almost or
altogether touch each other.—Ex. Spots in the margin of the Wings of
Argynnis Aglaia.
. Confluent (Confluens). When spots, &c. run into each other.—Ex. Apex
of the Primary Wings and Under side of the Secondary in Pontia
Daplidice.
. Obliterate (Obliterata). When the borders of spots fade into the general
ground-colour; and when elevations and depressions, &c. are so little
raised or sunk from the general surface, as to be almost erased.—Ex.
Streak in the Wings of Hipparchus papilionarius, &c. Striæ in the
Elytra of Sphodrus leucophthalmus.
. Obsolete (Obsoleta). When a spot, tubercle, punctum, &c. is scarcely
discoverable. Ex. Lycæna Hippothoe ♂ and ♀ .—N.B. This term is
often employed where one sex, kindred species, or genera, want, or
nearly so, a character which is conspicuous in the other sex, or in the
species or genus to which they are most closely allied.

. Geminous (Gemina). When there is a pair of spots, tubercles, puncta, &c.
—Ex. Head of one sex of Dorcus parallelopipedus. Upper Wings of
Odenestis potatoria.
. Didymous (Didyma). When this pair of spots, &c. touch or are confluent.
—Ex. Spots in Elytra of Tylostagmus quadrimaculatus.
. Connivent (Connivens). The meeting of two lines so as to form an angle.
—Ex. Streaks on the Under side of Secondary Wings of Thecla Pruni.
0. Common (Communis). Common to two. When a spot for instance is
partly on one elytrum and partly on the other.—Ex. Coccinella
septempunctata.

VIII. MARGIN.

. Crisp (Crispa). When the Limb is disproportionably larger than the Disk,
so as to render the margin uneven with irregular rises and falls.
. Undulate (Undulata). When the surface rises and falls obtusely, not in
angles.—Ex. Margin of Wings of Hipparchia Semele.
. Corrugate (Corrugata). When the surface rises and falls acutely in
angles.—Ex. Acidalia luteata, &c.
. Plicate (Plicata). Longitudinally or transversely folded; or so impressed
with striæ as to have that appearance.—Ex. Abdomen of Staphylinus.
. Dilatate (Dilatata). Dilated disproportionably with respect to the Disk.—
Ex. Prothorax of Necrophorus.
. Filate (Filata). When the edge is separated by a channel, often producing
a very slender threadlike margin.—Ex. Elytra of Choleva.
. Incrassate (Incrassata). When the margin is disproportionably thick.—
Ex. Mr. Marsham's Family of Chrysomela "thorace utrinque
incrassato."
. Intire (Integra). When the margin has neither teeth, serratures, nor other
incisions.

. Channel (Canalis). An impressed line more or less wide, which attends
the edges, and is usually produced by its reflexion.
0. Edge (Acies). The extreme termination of the margin.

IX. TERMINATION.

. Summit (Fastigium). The tip or extreme termination of the upper part.
. Apex (Apex). The top or upper termination of any part.
. Bottom (Fundus). The extreme termination of the lower part.
. Base (Basis). The lower termination of any part.
. Acute (Acuta). Terminating in an acute angle. Plate XV. Fig. 17.
. Obtuse (Obtusa). Terminating bluntly, but within the segment of a circle.
Plate XIV. Fig. 1. f.
. Rotundate (Rotundata). Terminating in the segment of a circle.—Plate
VI. Fig. 1. e.
. Truncate (Truncata). Terminating in a transverse line. Plate XIII. Fig. 5.
a´´´.
. Premorse (Præmorsa). Terminating in an irregular truncate apex, as if
bitten off.—Ex. Elytra of Lebia, Dromia, Lomechusa, &c.
0. Retuse (Retusa). Terminating in an obtuse sinus.—Ex. Back part of the
Head in Cimbex.
1. Emarginate (Emarginata). When the end has an obtuse notch taken out.
—Ex. Nose of Pedinus arenosus.
2. Exscinded (Excisa). When the end has an angular notch taken out.—Ex.
Nose of Opatrum sabulosum.
3. Producted (Producta). Disproportionably long.
4. Mucronate (Mucronata). Terminating suddenly in a strong point.—Ex.
Elytra of Lixus paraplecticus. Abdomen of Sirex Gigas ♀.

5. Acuminate (Acuminata). Terminating gradually in a sharp point.—Ex.
Abdomen of Sirex Juvencus ♀.
6. Apiculate (Apiculata). Terminating suddenly in a small filiform truncate
apex.—Ex. Abdomen of Thelyphonus.
7. Cuspidate (Cuspidata). Terminating in a long setiform point.—Ex. Tail
of Scorpio.

X. INCISION.

. Incised (Incisa). Cut into equal marginal segments.
. Cleft (Fissa). Cut into equal and deep segments, but not reaching the
base. Plate XIV. Fig. 3. a.
Bifid (Bifida). Cut into two segments.
. Trifid (Trifida). Cut into three.
Quadrifid (Quadrifida). Cut into four.
. Multifid (Multifida). Cut into more than four.
. Laciniate (Laciniata). Cut into unequal, irregular, and deep segments.
. Squarrose (Squarrosa). Cut into laciniæ that are elevated above the
plane of the surface.
. Partite (Partita). Divided to the base. Plate XIV. Fig. 3. b.
Bipartite (Bipartita). Divided thus into two parts.
. Tripartite (Tripartita). Divided into three parts.
Quadripartite (Quadripartita). Divided into four parts.
. Multipartite (Multipartita). Divided into more than four parts.
. Lobate (Lobata). Divided to the middle into parts with convex margins,
which recede from each other.—Ex. Acanthia paradoxa. Bilobate,
with two lobes. Trilobate, with three lobes, &c.

. Cruciate (Cruciata). Divided to the middle into four opposite arms, the
angles being either four right ones, or two obtuse and two acute.—Ex.
Prothorax of many Locustæ.
. Sinuate (Sinuata). Having large curved breaks in the margin resembling
bays. Plate XIV. Fig. 1.
. Erose (Erosa). Sinuate, with the sinuses cut out into smaller irregular
notches as if gnawed.—Ex. Wings of Vanessa C. album.
0. Crenate (Crenata). Cut into segments of small circles.
1. Serrate (Serrata). Cut into teeth like a saw, with teeth whose sides are
unequal.—Ex. External margin near the Apex of the Elytra of many
species of Buprestis.
2. Dentate (Dentata). Cut into teeth, with teeth whose sides are equal or
nearly so.—Ex. The Wings of many Butterflies.
3. Repand (Repanda). Cut into very slight sinuations, so as to run in a
serpentine direction. Plate XXII. Fig. 11. s.

XI. RAMIFICATION.

. Dichotomous (Dichotoma). Dividing regularly in pairs.
. Furcate (Furcata). Dividing into two. Plate XVIII. Fig. 11.
. Ramose (Ramosa). Furnished with lateral branches. Plate XI. Fig. 18.
. Decussate (Decussata). Sending forth lateral branches which alternately
cross each other.
. Divaricate (Divaricata). Standing out very wide.

XII. DIVISION.

. Segment (Segmentum). The great inosculating joints of the body.
. Joint (Articulus). The joints of a limb or member.
. Incisure (Incisura). A deep incision between the segments, when they
recede from each other.
. Suture (Sutura). The line of separation of any two parts of a crust which
are connected only by membrane or ligament, but do not inosculate.
Spurious Suture (Sutura spuria). An impressed line in any part of a body,
which resembles a suture, but does not really divide the crust.

XIII. DIRECTION.

. Longitudinal (Longitudinalis). Running lengthwise.
. Transverse (Transversa). Running across: when the longitudinal line is
cut through at right angles.
. Oblique (Obliqua). Running sideways. When the longitudinal line is cut
through at acute angles.
. Horizontal (Horizontalis). Parallel with the horizon.
. Erect (Erecta). Nearly perpendicular.

. Vertical (Verticalis). Perpendicular.
. Sloping (Declivis). A gentle descent.
. Descending (Descendens). A steeper descent.
. Acclivous (Acclivis). A gentle ascent.
0. Ascending (Ascendens). A steeper ascent.
1. Reclined (Reclinata). Leaning towards any thing as if to repose upon it.
2. Recumbent (Recumbens). Leaning or reposing upon any thing.
3. Reflexed (Reflexa). Bent back or upwards.
4. Inflexed (Inflexa). Bent inwards.
5. Recurved (Recurva). Curving outwards.
6. Incurved (Incurva). Curving inwards.
7. Revolute (Revoluta). Rolled outwards.
8. Involute (Involuta). Rolled inwards.
9. Forwards (Antrorsum).
0. Backwards (Retrorsum).
1. Upwards (Sursum).
2. Downwards (Deorsum).
3. Outwards (Extrorsum).
4. Inwards (Introrsum).
5. Straight (Recta).
6. Porrect (Porrecta). Reaching forth horizontally as if to meet something
advancing.
7. Broken (Fracta). Bent with an elbow, as if broken.

8. Converging (Convergens). Tending to one point from different parts.
9. Diverging (Divergens). Tending to different parts from one point.

XIV. SITUATION.

. Obverse (Obversa). When an object is viewed with its head towards you.
. Reverse (Reversa). When an object is viewed with its anus towards you.
. Resupine (Resupina). When an object lies upon its back.
. Prone (Prona). When an object lies upon its belly.

XV. CONNEXION.

. Colligate (Colligata). Adhering, or so fixed to any part as to have no
separate motion of its own.
. Free (Libera). Having a motion independent of that of the part to which
it is affixed.
. Connate (Connata). When parts that are usually separated, are, as it
were, soldered together, though distinguished by a suture.—Ex. Elytra
of Gibbium.
. Coalite (Coalita). When parts usually separate are distinguished neither
by incisure, segment, nor suture.—Ex. Trunk in Mutilla.
. Distinct (Distincta). When parts are separated from each other by a
suture.—Ex. Parts of the Trunk in Coleoptera, &c.
. Distant (Distans). When they are separated by an incisure.—Ex. Head,
Trunk, and Abdomen, in Hymenoptera.
. Inosculating (Inosculans). When one part is inserted into the cavity of
another.—Ex. Head in Buprestis.
. Suspended (Suspensa). When one part is joined to another by a ligature,
without being inserted in it.—Ex. Legs of Orthoptera.

XVI. ARMS.

. Tooth (Dens). A short flattish process, somewhat resembling a tooth.
. Horn (Cornu). A longer process, resembling a horn.
Laminate Horn (Cornu laminatum). A horn dilated at its base into a flat
plate.—Ex. Onthophagus nutans.
. Nodding Horn (Cornu nutans). When a horn bends forwards.—Ex.
Onthophagus nutans.
. Spine (Spina). A fine, long, rigid, pointed process.—Ex. Those on Elytra
of many Hispæ, and the Posterior Tibiæ of Locusta.
. Mucro (Mucro). A short, stout, sharp-pointed process.—Ex. Elytra of
Lixus paraplecticus.
. Spur (Calcar). A spine that is not a process of the crust, but is implanted
in it.—Ex. Those on the lower side of the Tibiæ of Acrida.

XVII. APPENDAGES.

. Auricle (Auricula). An appendage resembling an ear.—Ex. Thorax of
Ledra aurita.
. Caruncle (Caruncula). Having fleshy excrescences somewhat
resembling the caruncles of birds.—Ex. Prothorax of Malachius.

XVIII. MOTION.

. Vertical (Verticalis). When it is up and down.
. Horizontal (Horizontalis). When it is from side to side.
. Compound (Composita). When a part is capable of both vertical and
horizontal motion.
. Versatile (Versatilis). When it moves partly round as if upon a pivot.—
Ex. Head of Hymenoptera and Diptera.
. Vibratile (Vibratilis). When there is a constant oscillation of any part.—
Ex. Antennæ of the Chalcidites. Legs of Tipula when reposing.

. Rotatory (Rotatoria). When a body or a part of it turns wholly round, or
describes a circle.—Ex. Ants and Moths in a certain disease[1093].

XIX. SCENT.

. Acid (Acidus). A pungent acid scent.—Ex. Many Formicæ.
. Moschate (Moschatus). A scent of musk.
. Alliaceous (Alliaceus). A scent of garlic.—Ex. Some Andrenæ.
. Cimicine (Cimicinus). A scent like that of the Bed-bug.—Ex. Cimex.
. Rosaceous (Rosaceus). A scent of roses.—Ex. Cerambyx moschatus.
. Aromatic (Aromaticus). A pungent scent of spices.—Ex. Oxytelus
rugosus.
. Balm-scented (Melissæus).—Ex. The species of Prosopis (Apis *. b. K.).
. Sweet-scented (Odoratus). An undefined sweet scent.—Ex. Philonthus
suaveolens.
. Fetid (Fœtidus). A disagreeable scent.—Ex. Goerius olens. Chrysopa
Perla.

GENERAL RULES.
In the above tables no notice is taken of diminutives, compounds, and
similar terms, because it seemed best, with respect to these, to lay down
only some general rules which may include the whole.
Rule I.
Terms in English ending in cle, ule, or let, and which in Latin add lus, la, or
lum, to a word, diminish its sense. As, Denticle, a little tooth; Setule, a little
bristle; Eyelet, a small eye: Denticulus, a little dens; Guttula, a little gutta;
Punctulum, a little punctum. N.B. Where length or breadth are concerned,
the diminutive implies a diminution in the length of the predicate. As,
Lineola, Lineolet, a short line; Striola, Striolet, a short stria; Fasciola,
Fasciolet, a short fascia.

Rule II.
The preposition sub prefixed to any word reduces the sense of it. As,
Subpunctate, not fully punctate; Subhirsute, not fully hirsute, &c.
Rule III.
The termination culus in Latin words added to a comparative implies the
state of the object comparatively. As, Convexiusculus, rather convex than
not; Majusculus, rather large than not. This is usually denoted in English by
the termination ish, or the adverb rather; as, largish, rather large, &c.
Rule IV.
The participle present used instead of the adjective implies a tendency to the
quality expressed by it. As, Cinerascens, cinerascent, tending to cinereous,
&c.
Rule V.
The preposition ob prefixed to a term reverses it. As, Obconical, Obcordate,
a conical or heart-shaped body, of which the narrowest part is the base.
Rule VI.
In compound terms the last member indicates the preponderating character.
For instance, when it is said of a body that it is nigro-æneous, it means that
the æneous tint prevails: but if, vice versâ, it is termed æneo-nigrous, the
black tint is predominant.—N.B. In Sculpture the terms punctato-striate, or
punctato-sulcate, signify that striæ or furrows are drawn with puncta in
them.
Exception 1.
Some compound terms only indicate the union of two characters in one
subject. As, when we say of wings that they are cruciato-incumbent, we
mean both that they cross each other and are incumbent upon the body.
Exception 2.
Compound terms are sometimes employed very conveniently to restrict the
application of a character to particular circumstances. As, when we say

hirsuto-cinereous, we mean that the hirsuties only of a body is cinereous.
Rule VII.
When the term ordinary (ordinarius) is added either to terms expressing
impressed puncta, lines, spots, &c., it signifies that such puncta, lines, or
spots are common to a particular section in any genus or tribe. As, the
impressed lateral puncta on the thorax of Scarabæidæ; the lateral furrows
and dorsal channel in the ground beetles (Eutrechina), and the spots in the
primary wings of Xylina Polyodon and affinities[1094].
SYMBOLS.

Male ♂. Female ♀. Neuter ⚲. Egg θ. Larva ⊕. Pupa ☽. Imago ⊙. Head △.
Trunk □. Abdomen ▽[1095].

B. PARTIAL ORISMOLOGY.
I. BODY (corpus).

. Disjunct (Disjunctum). When head, trunk, and abdomen are separated by
a deep incisure.—Ex. Hymenoptera, Diptera. Plate IV. Fig. 2, 3, 5.
. Compact (Compactum). When head, trunk, and abdomen are not
separated by a deep incisure, but inosculate in each other.—Ex.
Buprestis, Elater, and many other Coleoptera, Orthoptera, and
Hemiptera.
. Bisect (Bisectum). When the head and trunk are not separated by a
suture, so that the insect consists only of two pieces.—Ex. Araneidea.
Plate V. Fig. 4.
. Coalite (Coalitum). When neither head, trunk, nor abdomen are
separated by any incisure or suture.—Ex. Many Acari L., Phalangium,
&c.
. Multisect (Multisectum). When an insect appears to have no distinct
trunk and abdomen, but is divided into numerous segments.—Ex.
Scolopendra; Iulus, &c. Plate V. Fig. 6.

. Cymbiform (Cymbiforme). When the margin of the thorax and elytra are
recurved so as to give a body the resemblance of the inside of a boat.
—Ex. Heleus, Cossyphus.

II. HEAD (caput).
i. DIRECTION.

. Prominent (Prominens). When the head is in the horizontal line, and
forms no angle with the trunk.—Ex. Carabus. Plate I. Fig. 1.
. Porrected (Porrectum). When the head is prominent and elongate.—Ex.
Cychrus.
. Nutant (Nutans). When the head forms downwards an obtuse angle with
the horizontal line, or trunk.—Ex. Harpalus.
. Cernuous (Cernuum). When the head forms downwards a right angle
with the trunk.—Ex. Most Gryllina and Locustina.
. Inflexed (Inflexum). When the head forms inwards an acute angle with
the trunk.—Ex. Blatta. Plate II. Fig. 3.
. Turreted (Turritum). When the head is producted into a kind of
columnar recurved turret or rostrum, in the sides of which, towards the
end, the eyes are fixed.—Ex. Truxalis.

ii. INSERTION.

. Retracted (Retractum). When the head is wholly withdrawn within the
trunk.—Ex. Parnus.
. Intruded (Intrusum). When the head is nearly withdrawn within the
trunk.—Ex. Melasis.
. Inserted (Insertum). When the head is partly withdrawn within the trunk.
—Ex. Buprestis.
. Exserted (Exsertum). When the head is quite disengaged from the trunk.
—Ex. Tenebrio, Blaps.

. Amplected (Amplexum). When the head is received into a sinus of the
thorax.—Ex. Hister.
. Recondite (Reconditum). When the head is wholly covered and sheltered
by the shield of the thorax.—Ex. Cassida, Lampyris.
. Semirecondite (Semireconditum). When the head is half covered by the
shield of the thorax.—Ex. Silpha, Cyphon.
. Retractile (Retractile). When an insect can at pleasure exsert its head, or
withdraw it within the trunk.—Ex. Hister, Larva of Lampyris.
. Versatile (Versatile). When the head can turn nearly round.—Ex.
Hymenoptera, Diptera.
0. Pedunculate (Pedunculatum). When the head is constricted behind into
a distinct neck.—Ex. Apoderus Coryli, &c.
1. Sessile (Sessile). When the head does not move in the socket of the
trunk, but is attached to it by a kind of ligament.—Ex. Hymenoptera,
Diptera.

iii. TERMINATION.

. Clypeate (Clypeatum). When the Nasus, Genæ, &c. are dilated so as to
shelter and overshadow the mouth.—Ex. Scarabæus, Copris, &c.
Plate XIII. Fig. 14.
. Capistrate (Capistratum). When the anterior part of the head is
attenuated and subelongated into a kind of flat rostrum or muzzle.—
Ex. Nitidula. Plate XIII. Fig. 13.
. Rostrate (Rostratum). When the anterior part of the head is elongated
and attenuated into a cylindrical or many-sided rostrum or beak.—Ex.
The weevils (Rhyncophora). Plate XIII. Fig. 12.
. Buccate (Buccatum). When the Nasus and anterior part of the head are
inflated.—Ex. Conops and other Diptera. Plate XIII. Fig. 16.

iv. APPENDAGES.

. Umbraculate (Umbraculatum). When there is upon the head an
umbrella-shaped process.—Ex. Gryllus umbraculatus.
. Lychnidiate (Lychnidiatum). When the Vertex, Frons, and Postnasus are
porrected so as to form a kind of rostrum which gives light in the
night.—Ex. Fulgora. Plate XIII. Fig. 15.

v. MOUTH (os).

. Terminal (Terminale). When the mouth terminates the head.—Ex.
Coleoptera, &c.
. Prone (Pronum). When the mouth is wholly under the head.—Ex.
Truxalis, Proscopia.
. Perfect (Perfectum). When the mouth is furnished with all the Trophi.
Viz. Labrum; Labium; Mandibulæ; Maxillæ; Maxillary and Labial
Palpi; and Tongue.—Ex. The Masticating Orders.
Feeders retracted (Trophi retracti). When, in a perfect mouth, the
Trophi are not capable of being much pushed out or drawn in.—Ex.
Most Coleoptera, Orthoptera, &c.
. Feeders retractile (Trophi retractiles). When, in a perfect mouth, the
Trophi can be considerably pushed forth or drawn in.—Ex. Stenus,
Apis, &c.
. Imperfect (Imperfectum). When the mouth wants any of the Trophi, or
they exist in it only as rudiments.—Ex. The Suctorious Orders.
. Elabrate (Elabratum). When an imperfect mouth has Mandibulæ,
Maxillæ, Labium, and Maxillary Palpi, or what perform their office,
but no Labrum.—Ex. Araneidea.
. Emandibulate (Emandibulatum). When an imperfect mouth has all the
Trophi but the Mandibulæ.—Ex. Trichoptera.
. Bipalpate (Bipalpatum). When an imperfect mouth has only either Labial
or Maxillary Palpi.—Ex. Tabanus, &c.

. Expalpate (Expalpatum). When an imperfect mouth has no Palpi.—Ex.
Hemiptera.
. Stomapodous (Stomapodum). When the Legs and Sternum act the part of
Maxillæ, Labium, and Palpi.—Ex. Araneidea, Scolopendra, &c.

a. upper lip (Labrum).

. Whiskered (Mystacinum). When the upper lip is furnished with whiskers
(Mystax), or bearded.—Ex. Creophilus hirtus. Plate XXVI. Fig. 30.

b. upper jaws (Mandibulæ).

. Chelate (Chelatæ). When the upper jaws are furnished at the end with a
chela or thumb.—Ex. Scorpio, Phalangium.
. Unguiculate (Unguiculatæ). When they are armed with a moveable
claw.—Ex. Araneidea. Plate VII. Fig. 10. c´.
. Buried (Sepultæ). When they are covered and quite concealed by the
upper lip.—Ex. Colliuris.
. Open (Apertæ). When they are not quite concealed by the upper lip.—Ex.
Most Coleoptera.
. Toothless (Edentulæ). When they are not armed with teeth.—Ex.
Apogonia gemellata. Plate XXVI. Fig. 22.
. Toothed (Dentatæ). When they are armed with teeth.—Ex. Cicindela.
Plate XXVI. Fig. 19.
. Suctorious (Suctoriæ). When they have an orifice by which they imbibe
their food.—Ex. Larva of Dytiscus, Myrmeleon, &c. Plate XIII. Fig. 6.

c. under jaws (Maxillæ).

. Simple (Simplices). When the under jaws have but one lobe.—Ex.
Hymenoptera. Plate VII. Fig. 2, 3. d´.
. Compound (Compositæ). When they have more than one lobe.—Ex.
Staphylinus and many other Coleoptera. Plate XXVI. Fig. 9, 10. d´´´.

e´´´.
. Adnate (Adnatæ). When they adhere to the lower lip through their whole
length.—Ex. Trichoptera. Plate VII. Fig. 1. d´.
. Adherent (Adhærentes). When they adhere to it only at their base.—Ex.
Coleoptera, Hymenoptera, &c. Plate VI. VII. Fig. 3. d´.
. Spinose (Spinosæ). When they are armed at the apex with spines.—Ex.
Libellulina. Plate VI. Fig. 12. f´´´.
. Dentate (Dentatæ). When they are armed with teeth.—Ex.
Melolonthidæ. Plate XXVI. Fig. 15. g´´.
. Pectunculate (Pectunculatæ). When the stipes below the feeler has a
row of minute spines set like the teeth of a comb.—Ex. Apis[1096].
. Disengaged (Liberæ). When they do not adhere to the lower lip at all, or
are only connected by membrane or ligaments.—Ex. Apis, &c. Plate
VII. Fig. 3. d´.
. Mandibuliform (Mandibuliformes). When they are hard and horny and
shaped like the upper jaws.—Ex. Melolonthidæ, Anoplognathidæ, &c.
Plate XXVI. Fig. 13, 15.
0. Unguiculate (Unguiculatæ). When they terminate in a moveable claw.
—Ex. Cicindela.

d. feelers (Palpi).

. Maniform (Maniformes). When they are chelate or furnished with a
finger and thumb.—Ex. Scorpio, Chelifer. Plate XV. Fig. 7.
. Pediform (Pediformes). When they resemble the legs either in structure
or use.—Ex. Araneidea, Acarina. Plate VII. Fig. 10. h´´.
. Antenniform (Antenniformes). When they are very long resembling
antennæ.—Ex. Hydrophilus, Bryaxis, Culex ♂.
. Unguiculate (Unguiculati). When they are armed with a claw at the end.
—Ex. Gonyleptes. Plate XIII. Fig. 1.

. Securiform (Securiformes). When the last joint of the feeler is triangular,
and the preceding joint is connected with the vertex of the triangle.—
Ex. Cleridæ. Plate XIII. Fig. 2. a.
. Lunulate (Lunulati). When the last joint is shaped like a half-moon or
crescent.—Ex. Oxyporus. Plate XIII. Fig. 4. a.
. Fasciculate (Fasciculati). When the feeler terminates in a bunch of very
slender laminæ.—Ex. Lymexylon flavipes. Plate XXVI. Fig. 3.
. Lamellate (Lamellati). When the last joint is divided into transverse
lamellæ.—Ex. Atractocerus. Plate XXVI. Fig. 1.
. Inflated (Inflati). When the last joint of the feeler is very large and
tumid.—Ex. Araneidea ♂. Plate XIII. Fig. 3.
0. Appendiculate (Appendiculati). When from one of the joints there
issues an accessory joint or appendage.—Ex. Atractocerus,
Trombidium. Plate XXVI. Fig. 1. a. Plate XXIII. Fig. 13. a.
1. Mammillate (Mammillati). When the last joint is very short, smaller
than the preceding one, and retractile within it.—Ex. Pæderus[1097].
2. Subulate (Subulati). When the last joint is short, and vastly smaller than
the preceding one.—Ex. Bembidium, Aleochara. Plate XXVI. Fig. 7.
3. Fusiform (Fusiformes). When the two last joints are conical, and the
base of the cones forms the point of union.—Ex. Trechus. Plate
XXVI. Fig. 8.
4. Heteromorphous (Heteromorphi). When the two intermediate joints are
vastly larger than the first and the last.—Ex. Cerocoma ♂ . Plate
XXVI. Fig. 2.

e. tongue (Lingua).

. Linguiform (Linguiformis). When the tongue is quite distinct from the
labium, usually retracted within the mouth, short and shaped
something like a vertebrate tongue.—Ex. Gryllina, Libellulina. Plate
VI. Fig. 6, 12. e´.

. Liguliform (Liguliformis). When it emerges from the labium, is short,
flat, and not concealed within the mouth.—Ex. Vespa and many
Hymenoptera. Plate VII. Fig. 2. e'.
. Tubulose (Tubulosa). When it emerges from the labium, is long and
tubular, and capable of inflation.—Ex. Apis. Plate VII. Fig. 3. e´.
. Setiform (Setiformis). A short minute sharp tongue discoverable between
the scalpella of a promuscis.—Ex. Cimex L. Plate VII. Fig. 14. e´.
. Palatiform (Palatiformis). When the tongue forms the inner surface of
the Labium, but is not separate from it.—Ex. Most Coleoptera.

vi. NOSE (nasus).

. Included (Inclusus). When the nose is included between the two sides of
the Postnasus which run towards the upper lip.—Ex. Geocorisæ.
. Vaulted (Fornicatus). When the nose is elevated, convex and hollow
underneath.—Ex. Vespa.

vii. CANTHUS.

. Entering (Intrans). When the Canthus takes a little angle or sinus out of
the eye.—Ex. The Capricorn beetles, Mylabris. Plate VI. Fig. 1. h´.
. Cleaving (Findens). When the Canthus cleaves the eye half through or
more.—Ex. The Petalocerous beetles.
. Dividing (Dividens). When the Canthus passes right through the eye and
divides it into two.—Ex. Gyrinus, Tetraopes.[1098] Plate XXVI. Fig.
36.
. Septiform (Septiformis). When the Canthus forms an elevated ridge or
septum.—Ex. Many Petalocerous beetles.

viii. EYES (oculi).

. Simple (Simplices). Eyes which do not consist of an aggregate of
hexagonal lenses.—Ex. Araneidæ, Scorpio, Phalangium. Plate VII.

Fig. 9. h.
Scattered (Sparsi). When simple eyes are separate from each other and
not arranged in a certain order.—Ex. Eyes of Caterpillars, and some
Scolopendræ.
Ordinate (Ordinati). When simple eyes are arranged in a certain order.—
Ex. Araneidea. Plate XXVI. Fig. 37.
Conglomerate (Conglomerati). When a number of simple eyes are
collected together so as to exhibit the appearance of a compound one.
—Ex. Iulus. Plate XIII. Fig. 11.
Dorsal (Dorsales). When they are placed on the back.—Ex.
Phalangium. Plate XXVI. Fig. 43. h.
. Compound (Compositi). Eyes which consist of an aggregate of hexagonal
lenses.—Ex. All the Winged Orders. Plate XIII. Fig. 10. and XXVI.
Fig. 38-42. h.
Sessile (Sessiles). Eyes that do not sit upon a footstalk.—Ex. Most
insects. Plate XXVI. Fig. 40, 41.
. Superior (Superiores). When they are placed in the upper part of the
head.—Ex. Libellulina.
. Lateral (Laterales). When they are placed in the side of the head.—Ex.
Apis.
Inferior (Inferiores). When they are placed in the lower side of the head.
—Ex. The lower pair in Gyrinus.
Posterior (Posteriores). When placed in the posterior part of the head.—
Ex. Locusta.
Anterior (Anteriores). When placed in the anterior part of the head.—
Ex. Crabro, Goerius olens, &c.
Medial (Medii). When placed in the middle part of the head.—Ex.
Harpalus, &c.

. Belting (Cingentes). When the eyes nearly meet both above and below
the head, so as to form a kind of belt round it.—Ex. Culex pipiens,
Cordylia Palmarum.
Immersed (Immersi). When they are quite imbedded in the head.—Ex.
The Melasoma or Darkling beetles.
Prominent (Prominuli). When they stand out from the head.—Ex.
Cicindela.
Columnar (Columnares). When they sit upon a short footstalk or pillar.
—Ex. Strepsiptera, Ephemera ♂. Plate XXVI. Fig. 38, 39. h.
Pedunculate (Pedunculati). When they sit upon a long footstalk which
also bears the antennæ.—Ex. Diopsis. Plate XIII. Fig. 9.
Operculate (Operculati). When the eyes are covered by an operculum.—
Ex. Xylina conspicillaris[1099].
Ciliate (Ciliati). When the margin of the socket of the eye is fringed with
hairs, so as to resemble an eyelash.—Ex. Apion vernale and
Malvarum.

ix. STEMMATA.

. Vertical (Verticalia). When they are placed in the Vertex.—Ex. Reduvius
personatus. Plate XXVI. Fig. 40. i.
. Frontal (Frontalia). When placed in the Frons.—Ex. Hymenoptera.
Plate VII. Fig. 2. i.
. Intraocular (Intraocularia). When placed in the space between the eyes.
—Ex. Cercopis, Ledra, &c. Plate XXVI. Fig. 42. i.
. Subocular (Subocularia). When placed in the space below the eyes.—
Ex. Fulgora laternaria. Plate XXVI. Fig. 41. i.
. Spurious (Spuria). A flat subdiaphanous space above the base of the
antennæ, which seems to represent them.—Ex. Blatta, Gryllus.

x. ANTENNÆ.

a. number.

. Dicerous (Dicera). Insects that have two antennæ.—Ex. Insects in
general.
. Acerous (Acera). Insects that have no antennæ.—Ex. The Acarina, &c.

b. situation.

. Preocular (Præoculares). When antennæ are inserted before the eyes.—
Ex. Chrysis.
. Interocular (Interoculares). When inserted any where between the eyes.
—Ex. Leptura, Haliplus.
. Inocular (Inoculares). When inserted in the Canthus of the eyes.—Ex.
The Capricorn beetles.
. Subocular (Suboculares). When inserted under the eyes.—Ex. Fulgora,
Nepa. Plate XXVI. Fig. 41. k.
. Extraocular (Extraoculares). When inserted without the eyes.—Ex.
Notonecta, Delphax.
. Rostral (Rostrales). When seated on a rostrum.—Ex. The
Rhyncophorous beetles.
. Superior (Superiores). When inserted in the upper surface of the head.—
Ex. Most insects.
. Inferior (Inferiores). When inserted under the head.—Ex. Copris, &c.

c. approximation.

. Distant (Distantes). When remote at their base.—Ex. Buprestis rustica.
. Approximate (Approximatæ). When they approach each other at their
base.—Ex. Donacia, Galeruca.
. Contiguous (Contiguæ). When they nearly or altogether touch each other
at their base.—Ex. Imatidium MacLeayanum.

. Connate (Connatæ). When united at their base.—Ex. Ceria. Plate XII.
Fig. 13.

d. proportion.

. Very short (Brevissimæ). When shorter than the head.—Ex. The
Muscidæ, &c.
. Short (Breves). When as long as the head.—Ex. Hister.
. Shorter (Breviores). When longer than the head and shorter than the
body.—Ex. Dytiscus.
. Mediocral (Mediocres). When of the length of the body.—Ex. Callidium
violaceum.
. Longer (Longiores). When longer than the body.—Ex. Monochamus
Sutor.
. Very long (Longissimæ). When much longer than the body.—Ex.
Acanthocinus ædilis.

e. direction.

. Intire (Integræ). When they have no elbow or angle.—Ex. Antennæ of
most Coleoptera.
. Broken (Fractæ). When the Clavola forms an angle with the Scapus.—
Ex. Curculio, Apis, &c. Plate XXV. Fig. 15.
. Geniculate (Geniculatæ). When they form an elbow in the middle but
not with the Scapus.—Ex. Meloe. Plate XII. Fig. 7.
. Straight (Rectæ). When they are without any angle, convolution, or
curvature. Plate XI. Fig. 5.
. Porrect (Porrectæ). When they are placed parallel with each other, and
in the same line with the body.—Ex. Trichoptera in flight.
. Excurved (Excurvæ). When they curve outwards.

. Incurved (Incurvæ). When they curve inwards.
. Decurved (Decurvæ). When they curve downwards.
. Recurved (Recurvæ). When they curve upwards.
0. Reflexed (Reflexæ). When they are bent back over the body.
1. Deflexed (Deflexæ). When they are bent downwards.
2. Convolute (Convolutæ). When they roll inwards. Plate XII. Fig. 6.
3. Revolute (Revolutæ). When they roll outwards.
4. Spiral (Spirales). When they are convoluted spirally. Plate XXV. Fig.
31.
5. Rigid (Rigidæ). When they are very stiff and inflexible.—Ex.
Libellulina, Fulgora. Plate XII. Fig. 12, 15.

f. reposition.

. Hidden (Receptæ). Antennæ which when the animal reposes, are hidden
under the head or trunk.—Ex. The Lamellicorns, Elater, Belostoma.
. Exposed (Apertæ). Antennæ which when the animal reposes are not
concealed.—Ex. Cerambyx.

g. figure and size.

. Setaceous (Setaceæ). Long flexile antennæ which taper somewhat from
the base to the apex. Plate XI. Fig. 1.
. Setiform (Setiformes). Short rigid antennæ which taper from the base to
the apex like a bristle. Plate XII. Fig. 14-16.
. Capillary (Capillares). Antennæ nearly as slender as a hair. Plate XI
Fig. 2.
. Filiform (Filiformes). Antennæ every where of an equal thickness. Plate
XI. Fig. 3.

. Thick (Crassæ). Antennæ disproportionably thick. Plate XII. Fig. 29.
. Incrassate (Incrassatæ). Antennæ disproportionably thick in any part: at
the base, middle, or apex. Plate XXV. Fig. 34, 19, 7.
Gradually Incrassate (Sensim Incrassatæ). When they grow gradually
thicker from the base to the apex. Plate XXV. Fig. 10.
. Suddenly Incrassate (Subito Incrassatæ). When they grow suddenly
thicker in any part. Plate XXV. Fig. 18, 19, 24.
. Broad (Latæ). Antennæ disproportionably wide. Plate XXV. Fig. 24.
. Dilated (Dilatatæ). When they are disproportionably wide in any part;
base, middle, or apex. Plate XXV. Fig. 12. Plate XII. Fig. 1, 20.
. Slender (Tenues). When they are disproportionably slender. Plate XI.
Fig. 2.
0. Attenuate (Attenuatæ). Antennæ disproportionably slender in any part;
base, middle, or apex. Plate XXV. Fig. 8, 21, 34.
Gradually Attenuate (Sensim Attenuatæ). When they grow gradually
more slender from the base to the apex. Plate XI. Fig. 7.
. Suddenly Attenuate (Subito Attenuatæ). When they grow suddenly
slender in any part. Plate XII. Fig. 1. Plate XXV. Fig. 18, 34.
1. Fusiform (Fusiformes). Antennæ thickest in the middle and tapering
more or less towards each extremity. Plate XI. Fig. 5. Plate XXV. Fig.
8.
2. Prismatic (Prismaticales). Antennæ with three nearly equal sides. Plate
XI. Fig. 6.
3. Ensiform (Ensiformes). Antennæ compressed and three-sided, with one
side much narrower than either of the others. Plate XI. Fig. 7.
4. Falciform (Falciformes). When the Clavola of the Antennæ grows
gradually narrower towards the apex, and is arcuate or incurved so as
to resemble a sickle. Plate XI. Fig. 8.

5. Nodose (Nodosæ). When antennæ have one, two, or more joints larger
than those which precede or follow them. Plate XII. Fig. 5.
6. Moniliform (Moniliformes). Antennæ consisting of oval or globular
joints so as to resemble a necklace of beads. Plate XI. Fig. 9.
7. Dentate (Dentatæ). Toothed with teeth whose sides are equal. Plate XI.
Fig. 10.
8. Serrate (Serratæ). Toothed with teeth whose sides are unequal like
those of a saw. Plate XI. Fig. 11. Plate XXV. Fig. 8.
9. Biserrate (Biserratæ). So toothed on each side. Plate XXV. Fig. 18.
0. Imbricate (Imbricatæ). When the summit of each joint is incumbent
upon the base of that which precedes it. Plate XI. Fig. 12.
1. Distichous (Distichæ). When the joints in general terminate in a fork.
Plate XI. Fig. 13.
2. Cirrate (Cirratæ). When the joints terminate in a pair of curling hairy
branches resembling tendrils. Plate XXV. Fig. 4.
3. Flabellate (Flabellatæ). When the antennæ on one side send forth from
the joints, except those at the base, long flat flexile branches, which
open and shut like the sticks of a fan. Plate XI. Fig. 17.
4. Biflabellate (Biflabellatæ). When they are flabellate on both sides.
Plate XXV. Fig. 11.
5. Pectinate (Pectinatæ). Antennæ furnished on one side with a number of
parallel stiff branches, resembling somewhat the teeth of a comb. Plate
XXV. Fig. 25. Plate XI. Fig. 14.
6. Bipectinate (Bipectinatæ). Pectinate on both sides. Plate XXV. Fig. 22.
7. Duplicato-pectinate (Duplicato-pectinatæ). Bipectinate with the
branches on each side alternately long and short. Plate XI. Fig. 15.
8. Ramose (Ramosæ). Antennæ furnished on one side with two or three
irregular longish branches. Plate XI. Fig. 18.

9. Furcate (Furcatæ). Antennæ divided at the end into two prongs or
branches. Plate XI. Fig. 19. Plate V. Fig. 3.
0. Bipartite (Bipartitæ). When they are divided to the base into two nearly
equal branches. Plate XXV. Fig. 20.
1. Palmate (Palmatæ). Very short antennæ which send forth externally a
few long finger-shaped branches, giving them some resemblance of a
hand. Plate XI. Fig. 24.
2. Irregular (Irregulares). When the joints of the antennæ vary so much
in size and shape that they cannot well be defined. Plate XI. Fig. 22.

h. termination.
α. versatile antennæ.

. Subulate (Subulatæ). When they terminate in a minute joint, much
slenderer than the preceding one. Plate XII. Fig. 16.
. Setigerous (Setigeræ). When they terminate in a bristle. Plate XII. Fig.
14, 15. Plate XXV. Fig. 29.
. Capillaceous (Capillaceæ). When they terminate in a fine capillary joint.
Plate XII. Fig. 1.
. Mucronate (Mucronatæ). When they terminate in a short point or mucro.
Plate XII. Fig. 2.
. Uncinate (Uncinatæ). When their apex is incurved so as to form a kind of
hook. Plate XII. Fig. 3.
. Unguiculate (Unguiculatæ). When they terminate in a hard horny
incurved sharp claw resembling those of the tarsi of insects. Plate
XXV. Fig. 16. a.
. Clavate (Clavatæ). When their apex grows gradually thicker. Plate XII.
Fig. 4. Plate XXV. Fig. 7, 14.
. Capitate (Capitatæ). When they terminate suddenly in a larger knob of
one or more joints. Plate XII. Fig. 8-10, and XXV. 1-3, 5, 6.

Fissile Knob (Capitulum fissile). When it is divided into several laminæ
which the insect can open and shut. Plate XXV. Fig. 1-3, 5.
Tunicate Knob (Capitulum tunicatum). When the laminæ, at least on one
side, appear to inosculate or to be imbedded in each other. Plate XII.
Fig. 8. Plate XXV. Fig. 5, 6.
Perfoliate Knob (Capitulum perfoliatum). When the joints of the knob
are connected by a pedicle, which has the appearance of passing
through them. Plate XII. Fig. 10.
Solid Knob (Capitulum solidum). When the knob consists of a single
joint, or if of more, exhibits very faint traces of their separation. Plate
XII. Fig. 9. Plate XXV. Fig. 33.
Inflated Knob (Capitulum inflatum). When the knob is disproportionably
large, and looks as if blown out. Plate XII. Fig. 28. Plate XXV. Fig. 9.

β. inversatile antennæ.

. Setigerous (Setigeræ). Antennæ furnished with a terminal bristle. Plate
XII. Fig. 14-16, 21, 22. Plate XXV. Fig. 29.
Globiferous (Globiferæ). When the setigerous joint is larger than the
preceding one, and globose. Plate XII. Fig. 12.
Angustate (Angustatæ). When the setigerous joint is not conspicuously
larger than the preceding one. Plate XII. Fig. 14, 15.
. Aristate (Aristatæ). Antennæ terminated by a variously shaped flat joint
longer and usually larger than the preceding one, laterally setigerous.
Plate XII. Fig. 21, 22.
Setarious (Setariæ). When the awn or bristle is naked. Plate XII. Fig. 21.
a.
Plumate (Plumatæ). When the awn is feathered. Plate XII. Fig. 22. a.
. Filate (Filatæ). When inversatile antennæ have neither a terminal nor a
lateral bristle. Plate XII. Fig. 17-20.

Simple (Simplices). When the last joint is exarticulate. Plate XII. Fig. 17,
18, 20.
Compound (Compositæ). When the last joint is itself obsoletely jointed.
Plate XII. Fig. 19. a.

i. pubescence.

. Verticillate (Verticillatæ). Antennæ beset with hair in whorls. Plate XII.
Fig. 27.
. Plumose (Plumosæ). Antennæ feathered on all sides with fine long hair.
Plate XII. Fig. 24.
. Ciliate (Ciliatæ). Antennæ fringed with parallel hairs on each side. Plate
XI. Fig. 16.
. Fimbriate (Fimbriatæ). Antennæ fringed with parallel hairs on one side.
. Barbate (Barbatæ). Antennæ hairy on one side. Plate XII. Fig. 26.
. Fasciculate (Fasciculatæ). Antennæ having several bundles of hair.
Plate XXV. Fig. 32.
. Scopiferous (Scopiferæ). When they are furnished with one or more
dense brushes of hair. Plate XII. Fig. 25. a. Plate XXV. Fig. 17.

k. articulation.

. Exarticulate (Exarticulatæ). Without visible articulations.
. Biarticulate (Biarticulatæ). Consisting of two joints.
. Triarticulate (Triarticulatæ). Consisting of three joints.
. Quadriarticulate (Quadriarticulatæ). Consisting of four joints.
. Multiarticulate (Multiarticulatæ). Consisting of many joints.

l. joints.

. Campanulate (Campanulatæ). Bell-shaped. When the joints are
obconical, with the vertex of the cone rounded.
. Pateriform (Pateriformes). When the joints are somewhat dilated and
very short, shaped something like a shallow bowl.
. Patellate (Patellatæ). When the whole joint is dilated and shaped
something like a patella or platter.—Ex. Prosopis dilatata (Melitta *.
b. K.) Plate XXV. Fig. 12. a.
. Lobate (Lobatæ). When they are expanded at the tip into a lobe.—Ex.
Belostoma, Cerocoma. Plate XI. Fig. 21, 22.
. Torulose (Torulosæ). When they are a little tumid.

m. appendages.

. Auriculate (Auriculatæ). When they have an ear-like process at their
base.—Ex. Gyrinus, Parnus. Plate XII. Fig. 29. a. Plate XXV. Fig. 28.
a.
. Appendiculate (Appendiculatæ). When they have one or two antenniform
processes at their base.—Ex. Otiocerus. Plate XXV. Fig. 29. b.

III. TRUNK (truncus).

. Monomerous (Monomerus). When the trunk has no suture or segment.—
Ex. Araneidea.
. Dimerous (Dimerus). When the trunk consists of two greater segments.—
Ex. Coleoptera, &c.
. Trimerous (Trimerus). When the trunk consists of three greater segments.
—Ex. Neuroptera, &c.
. Isthmiate (Isthmiatus). When an isthmus is formed between the
Prothorax and Elytra, either in consequence of the former being
constricted behind so as to form a neck, or the scutellum not being
interposed between the elytra at their base, or the chief part of the

mesothorax not being covered by the prothorax.—Ex. Clerus,
Passalus, and Spondylis.

i. MANITRUNK (manitruncus).
a. prothorax.

. Clypeiform (Clypeiformis). When the prothorax by its magnitude and
distinct separation forms one of the most conspicuous pieces of the
upper side of the trunk, so as nearly to represent the whole thorax; the
mesothorax and metathorax being mostly hidden by the elytra and
other organs for flight.—Ex. Coleoptera, Orthoptera, &c. Plate VIII.
Fig. 1, 10.
. Colliform (Colliformis). When the prothorax is short and narrow, and
not so conspicuous as the other pieces of the trunk.—Ex. Libellulina.
Plate IX. Fig. 6.
. Cerviculate (Cerviculatus). When the prothorax is elongate, attenuate,
and distinguished from the Antepectus by no suture; so as to form a
distinct and usually long neck. Plate III. Fig. 6.
. Evanescent (Evanescens). When no distinct prothorax is discoverable or
it is only represented by membrane.—Ex. Most Hymenoptera,
Diptera, &c.
. Marginate (Marginatus). When an impressed line or channel separates
the edge of the prothorax from the rest of its surface, and so forms a
margin.—Ex. Harpalus, &c.
. Immarginate (Immarginatus). When it has no such margin.—Ex. The
Rhyncophorous beetles.
. Explanate (Explanatus). When its sides are so depressed and dilated as
to form a broad margin.—Ex. Necrophorus, Silpha.
. Emarginate (Emarginatus). When a segment of a circle is taken out of its
anterior part for the reception of the head.

. Ambient (Ambiens). When this sinus is so large as to receive the whole
head.—Ex. Chilocorus.
0. Circumambient (Circumambiens). When its sides are elongated
anteriorly and curve inwards, their ends lapping over each other and
the head, so as to form a circle round the posterior part of the latter,
and leave a space open for the eyes to see objects above them.—Ex.
Heleus.
1. Clypeate (Clypeatus). When it quite covers and overshadows the head.
—Ex. Lampyris, Cassida, Cossyphus.
2. Cucullate (Cucullatus). When it is elevated into a kind of ventricose
cowl or hood which receives the head.—Ex. Dictyonota crassicornis.
Plate XIII. Fig. 18. a[1100].
3. Alate (Alatus). When its sides are expanded into a kind of wing.—Ex.
Dictyonota crassicornis.
4. Auriculate (Auriculatus). When it expands on each side into two
processes resembling ears.—Ex. Ledra aurita.
5. Angulate (Angulatus). When its sides or base jut out into one or more
angles.—Ex. Copris.
6. Cruciate (Cruciatus). When it has two elevated longitudinal
obtusangular lines, the angles of which approach each other in its
middle, so as nearly to form a St. Andrew's cross.—Ex. Locusta. Plate
XIII. Fig. 17.
7. Obvolving (Obvolvens). When there are neither ora nor suture to
separate it from the antepectus.—Ex. Stenus, Curculio L.
8. Pulvinate (Pulvinatus). When in consequence of being depressed in one
place, it seems to puff out in another.—Ex. Aleochara canaliculata,
picea, &c.
9. Producted (Productus). When behind it terminates in a long
scutelliform process which covers the Mesothorax, Metathorax, and
great part of the Abdomen.—Ex. Acrydium, Centrotus.

b. antepectus.

. Trachelate (Trachelatum). When of itself it forms a neck, the prothorax
being represented only by membrane.—Ex. Xiphydria.
. Unarmed (Inerme). When it has no prosternum.—Ex. The
Rhyncophorous beetles. 3. Armed (Armatum). When it has a
prosternum. N.B. These two last terms may be extended also to the
Medipectus and Postpectus. And also to the whole together. Thus, if
there was no Sternum at all, it should be called Pectus inerme; and if
one existed in all these divisions of the breast, it would be Pectus
armatum.

c. arm (Brachium).
α. cubit (Cubitus).

. Clypeate (Clypeatus). When a concavo-convex plate is affixed to the
outside of the cubit.—Ex. Crabro clypeatus, scutatus, &c. ♂ . Plate
XV. Fig. 3. a.
. Palmate (Palmatus). When towards the apex the cubit is armed laterally
with several divaricate spiniform teeth.—Ex. Scarites, Clivina. Plate
XV. Fig. 5.
. Digitate (Digitatus). When the apex of the cubit is divided into several
long teeth or fingers.—Ex. Gryllotalpa. Plate XV. Fig. 6.
. Dolabrate (Dolabratus). When the apex of the cubit is dilated and
shaped something like the head of a hatchet. Plate XV. Fig. 4.

β. hand (Manus).

. Patellate (Patellata). When several joints of the hand are dilated so as to
form an orbicular patella furnished underneath either with suckers, or a
dense brush of hairs.—Ex. Dytiscus ♂, Staphylinus. Plate XV. Fig. 9.
. Scutate (Scutata). When a single joint of the hand is dilated into a broad
scutiform plate.—Ex. Hydrophilus piceus ♂. Plate XV. Fig. 8.