ix. As insects often live longest in the state we are treating of,

I shall say something next upon the _age_ of larvæ, or the period intervening between their exclusion from the egg and their becoming pupæ. This is exceedingly various, but in every case nicely adapted to their several functions and modes of life. The grubs of the flesh-fly have attained their full growth, and are ready to become pupæ, in _six_ or _seven_ days; the caterpillar of _Argynnis Paphia_, a butterfly, in _fourteen_ days; the larvæ of bees in _twenty_ days; while those of the great goat-moth (_Cossus ligniperda_) and of the cockchafer (_Melolontha vulgaris_) live _three_ years, or at least survive three winters, before the same change. That of another lamellicorn beetle (_Oryctes nasicornis_ F.) is said to be extended to _four_ or _five_; that of the wire-worm (_Elater segetum_) to _five_. That of the stag-beetle (_Lucanus Cervus_) is affirmed by Rösel to be extended to _six_ years; but the most remarkable instance of insect longevity is recorded by Mr. Marsham in the _Linnean Transactions_[489]. A specimen of _Buprestis splendida_, a beautiful beetle never before found in this country, made its way out of a deal desk in an office in London in the beginning of the year 1810, which had been fixed there in the year 1788 or 1789; so that according to every appearance it had existed in this desk more than twenty years. Ample allowance being made for its life as a pupa, we may conclude that it had existed as a larva at least half the above period. The grubs of the species of the genus _Cynips_ L. attain their full size in a short time; but they afterwards remain five or six months in the gall before they become pupæ[490].

With few exceptions it may be laid down, that those larvæ which live on dead animals, in fungi, in dung, and in similar substances, are of the shortest duration in this state; and that those which live under the earth, on the roots of grass, &c. and in wood, the longest: the former becoming pupæ in a few days or weeks, the latter requiring several months, or even years, to bring them to maturity. The larvæ which live on the leaves of plants seem to attain a middle term between the one and the other,--seldom shorter than a few weeks, and rarely longer than seven or eight months. Aquatic larvæ appear to be subject to no general rule: some, as the larvæ of _Gnats_, becoming pupæ in two or three weeks; and others, as those of the _Ephemeræ_, which are thus compensated for their short life as flies, in as many years[491]. The cause of all these differences is obviously dependent on the nature of the food, and the purposes in the economy of creation to which the larvæ are destined.

x. The last part of the history of larvæ relates to their _Preparations for assuming the pupa state_. When they have acquired their full size, after having ceased to take food, by a copious evacuation they empty the intestinal canal, even rejecting the membrane that lines it and the stomach[492]; their colours either change totally, or fade; and they make themselves ready for entering upon a new stage of their existence. Some merely rest in a state of inactivity in the midst of the substances in which they feed, as if conscious of their inability to select any safer abode. Of this description are most Coleopterous, Hymenopterous, and Dipterous larvæ, that feed under ground, or in the interior of trees, fruits, and seeds.

But a still larger tribe, those which feed on leaves, animals, &c. act as if more sensible of the insecurity of this to them important epoch. They are about to exchange their state of vigour and activity for a long period of deathlike sleep. The vigilant caution which was wont to guard them from the attack of their enemies will be henceforward of no avail. Destitute of all the means of active defence, their only chance of safety during their often protracted night of torpor must arise from the privacy of their place of repose. About this, therefore, they exhibit the greatest anxiety. Many, after wandering about as if bewildered, retire to any small hole on the surface of the earth, covering themselves with dead leaves, moss, or the like, or to the chinks of trees, or niches in walls and other buildings, or similar hiding-places. Many penetrate to the depth of several inches under ground, and there form an appropriate cavern by pushing away the surrounding earth; to which they often give consistence by wetting it with a viscid fluid poured from the mouth. The larvæ of other insects undertake long and arduous journeys in search of appropriate places of shelter. Those of flesh-flies, now satiated with the mass of putridity in which they have wallowed, leave it, and conceal themselves in any adjoining heap of dust. The grubs of the gad-fly (_Œstrus_) creep some of them out of the backs of cattle, in tumours of which they have resided, and suffer themselves to fall to the earth; while others, which have fed in the stomach of horses, quit their hold, and by a still more extraordinary and perilous route are carried through the intestines the whole length of their numerous circumvolutions, and are discharged at the anus. And without enumerating other instances, various aquatic larvæ, as that of a common fly (_Elophilus pendulus_), &c. leave the water, now no longer their proper element, and betake themselves to the shore, there to undergo their metamorphosis.

Most of these, having reached their selected retreat, require no other precaution; but another large tribe of larvæ have recourse to further manœuvres for their defence before they assume the pupa. Those of the aphidivorous flies (_Syrphus_ F. &c.), of the various lady-birds (_Coccinella_ L.), and tortoise-beetles (_Cassida_ L.), &c. fix themselves by the anus with a gummy substance to the leaves or twigs under which they propose to conceal themselves during their existence in that state. Others previously suspend themselves by a silken thread fixed to the tail, or passing round the body; by which also, when become pupæ, they are afterwards pendent in a similar position; and lastly, a very great number of larvæ wholly inclose themselves in cases or cocoons, composed of silk and various other materials, by which during their state of repose they are protected both from their enemies and the action of the atmosphere. As these two last-mentioned processes are extremely curious and interesting, I shall not fear tiring you by entering into some further detail respecting them: explaining _first_ the mode by which larvæ _suspend_ themselves, both before and after they are become pupæ, by silken threads; and _next_, the various _cases_ or _cocoons_ in which others inclose themselves, and their manner of operating in the formation of them.

1. The larvæ which suspend themselves and their pupæ, with the exception of the tribe of _Alucitæ_, and some _Geometræ_ of the family of _G. pendularia_, _punctaria_, &c. are almost all _butterflies_[493]. No others follow this mode. They may be divided into two great classes--those which suspend themselves _perpendicularly_ by the _tail_, and those which suspend themselves _horizontally_ by means of a thread girthed round their _middle_. In both cases it should be observed, that the suspension of the pupa is the object in view; but as the process is the work of the larva, this seems the proper place for explaining it. To begin with the _first_ case.

You are aware that all _lepidopterous_ larvæ have the faculty of spinning silk threads from their mouths, and it will readily occur to you that it is by means of these threads that they suspend themselves. But how? How is a caterpillar to hang itself by the tail to threads spun from the mouth? Even suppose this difficulty overcome, others still greater remain. Suppose the caterpillar to be suspended by its tail,--this is but a preparatory operation,--what is required is, that the pupa shall hang in the same position: now when you take into consideration that it is incased _within_ the skin of the larva, and without feet or other external organs; that it has to extricate itself from this skin; to hang itself in its place, and to detach the skin from the threads which hold it--this will appear no trifling task. Indeed at first view it seems impossible. Country-fellows for a prize sometimes amuse the assembled inhabitants of a village by running races in sacks: take one of the most active and adroit of these, bind him hand and foot, suspend him by the bottom of his sack with his head downwards, to the branch of a lofty tree; make an opening in one side of the sack, and set him to extricate himself from it, to detach it from its hold, and suspend himself by his feet in its place. Though endowed with the suppleness of an Indian juggler, and promised his sack full of gold for a reward, you would set him an absolute impossibility: yet this is what our caterpillars, instructed by a beneficent Creator, easily perform. Their manœuvres I shall now endeavour to explain.

When the caterpillar has selected the under-side of the leaf or other object to which it purposes suspending itself, its first process is to spin upon it a little hillock of silk consisting of numerous loosely interwoven threads; it then bends its body so as to insinuate the anal pair of prolegs amongst these threads, in which, by a slight exertion, the little crochets which surround them[494] become so strongly entangled as to support its weight with ease. It now suffers the anterior part of the body to fall down, and it hangs perpendicularly from its silken support with its head downwards. In this position it remains often for twenty-four hours, at intervals alternately contracting and dilating itself. At length the skin is seen to split on the back near the head, and a portion of the pupa appears, which by repeated swellings acts like a wedge, and rapidly extends the slit towards the tail. By the continuance of these alternate contractions and dilatations of the conical pupa, the skin of the caterpillar is at last collected in folds near the tail, like a stocking which we roll upon the ancle before withdrawing it from the foot. But now comes the important operation. The pupa, being much shorter than the caterpillar, is as yet at some distance from the silken hillock on which it is to be fastened; it is supported merely by the unsplit terminal portion of the latter's skin. How shall it disengage itself from this remnant of its case, and be suspended in the air while it climbs up to take its place? Without arms or legs to support itself, the anxious spectator expects to see it fall to the earth. His fears, however, are vain; the supple segments of the pupa's abdomen serve in the place of arms. Between two of these, as with a pair of pincers, it seizes on a portion of the skin; and bending its body once more, entirely extricates its tail from it. It is now wholly out of the skin, against one side of which it is supported, but yet at some distance from the leaf. The next step it must take is to climb up to the required height. For this purpose it repeats the same ingenious manœuvre, making its cast-off skin serve as a sort of ladder, it successively with different segments seizes a higher and a higher portion, until in the end it reaches the summit, where with its tail it feels for the silken threads that are to support it. But how can the tail be fastened to them? you ask. This difficulty has been provided against by Creative Wisdom. The tail of the pupa is furnished with numerous little hooks pointing in different directions[495], as well adapted to the end in view as the crochets of the larva's prolegs, and some of these hooks are sure to fasten themselves upon the silk the moment the tail is thrust amongst it. Our pupa has now nearly completed its labours; it has withdrawn its tail from the slough, climbed up it, and suspended itself to the silken hillock--manœuvres so delicate and perilous, that we cannot but admire that an insect which executes them but once in its life, should execute them so well: nor could it, as Reaumur has well and piously observed, had it not been instructed by a GREAT MASTER. One more exertion remains: it seems to have as great an antipathy to its cast-off skin, as one of us should, when newly clothed after a long imprisonment, to the filthy prison garments we had put off. It will not suffer this memento of its former state to remain near it, and is no sooner suspended in security than it endeavours to make it fall. For this end--it seizes, as it were with its tail, the threads to which the skin is fastened, and then very rapidly whirls itself round, often not fewer than twenty times. By this manœuvre it generally succeeds in breaking them, and the skin falls down. Sometimes, however, the first attempt fails: in that case, after a moment's rest, it makes a second, twirling itself in an opposite direction; and this is rarely unsuccessful. Yet now and then it is forced to repeat its whirling, not less than four or five times: and Reaumur has seen instances where the feet of the skin were so firmly hooked, that after many fruitless efforts the pupa, as if in despair, gave up the task and suffered it to remain[496]. After these exertions, it hangs the remainder of its existence in this state until the butterfly is disclosed.

We are now to consider the _second_ mode of suspension, in which larvæ by means of a silken girth round their middle, fix themselves _horizontally_ under leaves, &c. These follow the same process with that of those last described, in spinning a small hillock of silk to which they fasten their hind legs; and if the operation concerned the larva state alone, this would be sufficient, as by means of this support, and of their prolegs, they could easily retain themselves in a horizontal position. But these larvæ act as if they foresaw the assumption of a state in which they will be deprived of legs. It is the suspension of the forthcoming pupa that is the object in view; and though this can be hung by the tail in the same way with those of the first class, yet it is plain that it cannot be retained in a horizontal position, which for some unknown reason is essential to it, without some support to its anterior extremity. It is necessary for the larva, therefore, not only to fix its posterior legs amongst a collection of silken fibres, but to spin a _girth_ of the same material round its body. This girth, though apparently of a single thread, will be found on examination to be composed of several, often as many as fifty or sixty; and is fastened on each side of the body of the larva about the middle, to the surface under which it is placed. Three different modes of fixing these girths are adopted by the caterpillars of different butterflies. Some, as those of the common cabbage-butterfly (_Pieris Brassicæ_), which have remarkably pliable bodies, bend them almost double on one side, then fix the thread and carry it over to the other in the same position, repeating this operation as often as is necessary. Others, as that of _Lycæna Argus_ and many more of the _Papiliones Rurales_ and _Urbicolæ_ L., which have a short and more rigid body, after having bent the head on one side so as to fix one end of the thread, bring themselves into a straight position, and, by a manœuvre not easily described, contrive to introduce the head under the thread, which they then bend themselves to fasten on the other side, pushing it to its proper situation by the successive tension and contraction of their segments. But the most curious mode, though indeed that which seems most natural, is adopted by the caterpillar of the beautiful swallow-tail butterfly (_Papilio Machaon_) and others of the same family. This first forms the loop which is to serve for its girth, and then creeps under it. But the difficulty it has to surmount is, to keep itself from being entangled in the fifty or sixty fine distinct threads of which the girth is composed, and to preserve them all extended so as to be able to introduce its body beneath them. For this purpose it makes use of the two first pair of its fore-legs, employing them as a woman does her hands in winding a skein of cotton, to collect and keep all the threads of its card unentangled and properly stretched; and it is often with great difficulty, towards the end of the process, that it prevents them from slipping off. When a sufficient number of threads is completed, the animal bends its head between its legs, and insinuates it under the collected loop, which by its annular contraction it easily pushes to the middle of the body.

In about thirty hours after the larvæ which girth themselves have finished their operations, the skin splits, and the pupa disengages itself from it by those contractions and dilatations of its segments which have been before described, pushing the exuviæ in folds to the tail, by different motions of which it generally succeeds in detaching them. One would have thought there would be considerable difficulty in slipping the skin past the girth; but this, according to Reaumur, seems to be easily effected[497].

If you are desirous of witnessing for yourself the manœuvres by which these curious modes of suspension are effected, you may be readily gratified. It is only necessary to collect and feed until their metamorphosis the black spinous caterpillars of the common peacock-butterfly (_Vanessa Io_), which in most places may be found upon nettles, or those of the _Pieris Brassicæ_, which swarm in cabbages or brocoli in every garden. The former will exhibit to you a specimen of _vertical_, the latter of _horizontal_ suspension. It should be observed, however, that to hit the precise moment when these processes are going on, it is necessary to feed a considerable number of the larvæ of each kind; some one of which, if you watch them narrowly when they have attained their full growth, you will scarcely fail to surprise in the act.

I must observe here, that although the vertical and horizontal are the two principal positions in which caterpillars suspend themselves, yet that others are inclined at various angles; and some are attached with less art, appearing only to be fastened by some part of their abdomen to the body upon which they are fixed[498].

2. The larvæ whose procedures I am in the next place to describe, are those which, previously to assuming the pupa state, inclose themselves in _cases_ or _cocoons_ of different materials. For the sake of method, I shall divide these into two great classes: _First_, those which form their cocoons entirely or principally of _silk_; and _secondly_, those which form them chiefly of _other substances_.

To begin with the _first_. The larvæ which inclose themselves in _silken_ cocoons are chiefly of the Lepidopterous tribes of _Bombycidæ_ and _Noctuidæ_; but a few _Geometræ_ (_G. papilioniaria_, _lactearia_, &c.); most of the _Hymenoptera_; some _Coleoptera_, as certain of the weevil tribe (_Hypera Arator_, _Rumicis_ Germ.), and those brilliant beetles frequenting aquatic plants constituting the genus _Donacia_ F.; the Neuropterous genera _Hemerobius_ and _Myrmeleon_; _Mycetophila_ and a few others in the _Diptera_; and _Pulex_ in the _Aphaniptera_ fabricate coverings of the same material. In all, with the exception of _Myrmeleon_ and _Hemerobius_ (and perhaps _Hypera Rumicis_, &c.?) which have their spinning apparatus at the extremity of the abdomen, the silken thread employed in forming these coverings proceeds from the middle part of the under-lip, as before explained; and is in fact composed of two threads gummed together as they issue from the two adjoining orifices of the spinner.

Of the larvæ which inclose themselves in _silk_, the most familiarly known is the silk-worm: the cocoon of this consists exteriorly of a thin, transparent, gauze-like coating, through the interstices of which can be seen an inner, smaller, oval ball of a more close and compact texture. The whole is in fact composed of one single thread, but arranged in two distinct modes. To form the _exterior_ envelope, which is merely the scaffolding by means of which the inner and more solid covering is constructed, the caterpillar, after fixing upon a space between two leaves or twigs or angles suitable for its purpose, begins by glueing one end of its thread to one of the adjoining surfaces. This thread it next conducts to another part and then fastens, repeating this process and interlacing it in various directions, until it has surrounded itself with a slight and loosely spun netting. In the centre of this, when contracted into a space sufficiently small, it lays the foundation of the _interior_ cocoon. Fixing itself by its prolegs to some of the surrounding threads, it bends its body, and by successive motions of its head from side to side spins a layer of silk on the side opposite to it: when this is of the requisite thickness, the larva shifts its position, and repeats the same process in another quarter, covering each layer in turn with a new one until the interior cavity is reduced to the size desired. Thus, the silken thread which forms this new cocoon is not, as might have been supposed, wound circularly as we wind the thread of a ball of cotton; but backwards and forwards in a series of zigzags, so as to compose a number of distinct layers. Malpighi could distinguish six of these layers[499], and Reaumur suspects there is often a greater number[500]. The former found the length of the thread of silk composing them when wound off, without including the exterior case, to be not less than 930 feet[501]; but others have computed it at more than a thousand[502]: consequently the threads of five cocoons united would be a mile in length. Estimating by the weight,--the thread of a pound of cocoons, each of which weighs about two grains and a half, would extend more than 600 miles[503], and such is its tenuity, that the threads of five or six cocoons require to be joined to form one of the thickness requisite in the silk manufacture. It is the continuous thread of the inner cocoon which is most valuable; the outer loose coating from its irregularity cannot be wound off, and is known in commerce by the name of _floss silk_.

Manœuvres in their general principle similar to those of the silk-worm are followed by most of those larvæ which inclose themselves in silken cocoons. Many species, however, adopt variations in the mode of procedure all of which it would be tedious to particularize, but some of them are worth mentioning. The larvæ of _Tortrix prasinana_, and other species of moths which form cocoons resembling a reversed boat, arrange their threads in layers, so as to construct two parallel walls gradually inclining towards the top and ends, where they finally force them to approach each other by means of an apparatus of silken cables[504]. And the larva of _Saturnia Pavonia_, though it forms the base of its flask-shaped cocoon by spinning like the silk-worm a number of interwoven zigzags, places the threads which compose the interior funnel-like opening of the apex nearly straight, parallel to each other, and converging towards the same point in the centre[505].

These last, as well as almost all larvæ, constantly remain in the _inside_ of the cocoon during its construction. But De Geer has given us the history of a minute caterpillar of a species of moth (_Tinea_ L.) which feeds on the under side of the leaves of the _Rhamnus Frangula_, or Black Alder, that actually weaves half of its cocoon on the _outside_. This cocoon, which is very small, is beautifully fluted, consisting of several longitudinal cords, with the intervals filled by fine net-work, and shaped like a reversed boat[506]. The animal begins by laying the foundations of one of the ends of her cocoon, she adds new threads to this small beginning, and so proceeds. As the work advances she retreats backwards, and her body is situated nearly in the same line with the cocoon she has begun, and quite _out_ of it; she only touches with her head and legs its anterior margin. When half the cocoon, or rather of its exterior layer, is finished, she suspends her operations for some moments. She then for the first time introduces her head _into_ this demi-cocoon, and turns herself in it by doubling her supple body, and passing one part over the other, so that at last she manages to bring her tail into the pointed end of the cocoon, the head and the anterior half of her body remaining without. Thus situated, she commences her operations afresh. At a distance from the margin of the demi-cocoon, equal to its length, she begins to spin the pointed end of the other moiety, the length of her body serving her as a measure that enables her to begin at the proper distance from it. This new portion she spins in the same manner as the other; but as she is prevented by the demi-cocoon in which the posterior part of her body is lodged from retreating backwards, she contracts her body more, which answers the same purpose. When the new work is so advanced that she can no longer contract her body, she bends the anterior part of it considerably, and reverses her head. When the distance between the margin of the two halves of the cocoon is very small, so as no longer to admit the head between them, in order to unite them she is obliged to have recourse to another manœuvre. Withdrawing her head, she extends silken longitudinal threads between the two margins, and thus unites them. This part is more clumsy, and not so regular as the rest of the cocoon, so that the point of union is always discoverable. These caterpillars do not always divide the cocoon into two _equal_ portions, for often they will finish three quarters of the cocoon before they enter it, and begin at the other end[507].

The general rule is,--that each larva spins for itself a separate cocoon; but amongst those of _Arctia chrysorhea_ and others which live in society, two or three sometimes begin their operations so close together that they are under the necessity of forming one common cocoon, which serves for a covering to the whole number. The same thing happens to silk-worms, the double or treble cocoons of which are called _Dupions_ by the breeders. The larvæ of some Ichneumons, besides forming each its separate cocoon, spin a joint cottony covering for the whole[508], which is effected thus:--After they leave the caterpillar they have devoured, they fix themselves side by side at a little distance from it, and begin to spin each a cocoon; and in order to defend its end and side that is not covered by others, they spin further an envelope of loose silk, and thus this exterior covering is formed.

The size, figure, colour, substance, and texture of silken cocoons are extremely various. Their _size_ indeed is usually proportioned to that of the included larva or pupa; yet it is by no means always so. Some large caterpillars spin cocoons so small, that the observer can hardly conceive how they can be contained in so narrow a compass: _Eriogaster Catax_ is a moth of this description[509]. And others smaller in size lodge themselves in apartments apparently much more spacious than necessary. The transparent hammock-like cocoons of _Hepialus Humuli_ and _Arctia villica_, two other moths, would contain several of their pupæ. I possess one in which the pupa is suspended in the centre, that is ten times its size, and not very short in dimensions of that of _Attacus Paphia_, a giant silk-moth. The largest cocoon I ever read or heard of, is that thus described by Mr. Hobhouse in his _Travels_: "Depending," says he, "from the boughs of the pines, near the Attic mountain Parnes, and stretching across from tree to tree so as to obstruct our passage, were the pods, _thrice as big as a turkey's egg!_ and the thick webs of a chrysalis, whose moth must be far larger than any of those in our country."[510] If this statement is correct, and I am not aware that there is any reason for doubting it, the cocoon must be vastly larger than the pupa, or the moth it produced would far exceed in size any yet known. Perhaps, however, as this gentleman is probably no entomologist, what he took for a cocoon might be a nidus, in which many larvæ were associated, of the nature of those formerly described[511].

With regard to _figure_, the majority are like those of the silk-worm, of a shape more or less oval or elliptic: some, however, vary from this. That of _Lasiocampa Rubi_ is oblong. I have one from New Holland somewhat resembling an acorn, fixed to the twigs of some tree or shrub, of a very close silk, and covered by a circular operculum, which the animal pushes off when it assumes the imago; this is ovate or conico-ovate; others again are globose[512]; others are conical[513], as that of _Gastropacha quercifolia_; others almost fusiform[514] (_Odenesis potatoria_). Reaumur received one from Arabia which was nearly cylindrical[515]. Those of _T. prasinana_ before noticed, and many other _Tortrices_, are shaped like a reversed boat[516]; that of _Saturnia Pavonia_ and others of the same tribe, like a Florence flask with a wide and short neck. The cocoon of _Lygæna Filipendulæ_ resembles a grain of barley. Another cocoon in my cabinet, of very slight network, is shaped something like an air-balloon. But the most remarkable one for its form and characters, is one that I received from the rich cabinet above quoted. This, which is of an unusually close texture, is suspended by a thread more than two inches long from the point of a leaf; it then swells into a perfect cone, at the base about four-fifths of an inch in diameter and half an inch in length, and covered with scattered setiform appendages: from the centre of the base projects a large hemispherical protuberance, which terminates in a long stalk, much thicker than the thread that suspends the cocoon. There is commonly no difference between the shape of cocoons spun by larvæ which are to give birth to different sexes of the same species. The silk-worm cocoons, however, which will produce _male_ moths, have more silk at the ends, and consequently are more round than those which are to produce _females_: but the difference is not striking.

The most usual _colour_ of silken cocoons is white, yellow, or brown, or the intermediate shades. The whites are very pure in the general envelope of some species of _Ichneumonidæ_, and yellows often very brilliant. But besides these more general colours, some cocoons are black[517], some few blue or green, and others red[518]. Sometimes the same cocoon is of two different colours. Those of certain parasites of the tribe of _Ichneumones minuti_ L. the motions of one of which I noticed on a former occasion[519], are alternately banded with black or brown and white, or have only a pale or white belt in the middle, which gives them a singular appearance. In both cases the difference in colour depends upon the different tints with which the silky gum is imbued in the reservoirs: the first portion of it is white, and with this the larva first sketches the outline of its cocoon, and then thickens the layers of silk considerably in those parts where the white bands appear: when these are finished, its stock of white silk is exhausted, and the remainder of the interior of the cocoon is composed of brown silk[520]. The circular operculum above mentioned as covering an acorn-shaped cocoon, is paler than the latter, and also ornamented by a zone within the margin of deep brown. The pale cocoon also of _Attacus Paphia_ is veined with silk of a deep red.

I have very little to say on the _substance_ of the silk of cocoons. Though that of the silk-worm is composed of such a slender thread, that of many others is still finer, scarcely yielding in tenuity to the spider's web. On the other hand, the silk of the cocoons of _Saturnia Pavonia_ and of several foreign species is as thick as a hair.

With regard to the _texture_ of their cocoons--in some, as in that of the silk-worm, the threads are so slightly glued to each other, as to separate with facility; but in that of the emperor-moth just mentioned they are intimately connected by a gummy matter, furnished, as Reaumur conjectures, from the anus[521], with which the whole interior of the cocoon is often plastered. Some, as that of the silk-worm, are composed of an exterior loose envelope, and an inner compact ball; others have no exterior covering, the whole cocoon being of an uniform and thick texture. The larva of _Cossus Robiniæ_ Peck, in spinning its cocoon, makes the end next the opening to the air, by which the imago is to emerge, of a slighter texture than the rest of it[522]. The exterior case is sometimes, as in _Laria pudibunda_, very closely woven, so as to resemble a real cocoon[523]: its form is usually adapted to that of the inner one; but in some which fix them under flat surfaces (_Laria fascelina_, _Callimorpha Caja_,) it resembles a hammock[524]. Cocoons of a close texture have generally no orifice in any part; but that of _Eriogaster lanestris_ is spun with openings, as if bored from without, the use of which, however, does not seem to have been ascertained[525].

Many silken cocoons are of so close a fabric, as, when finished, entirely to conceal the included insect; but a very considerable number are of a more open texture, composed of a much smaller quantity of silk, and that woven so loosely, that the larva or pupa may always be discovered through it. Of this description are the cocoons of _Hypogymna dispar_, _Arctia Salicis_, &c., which consist only of a few slight meshes. Those of some others resemble gauze or lace[526]. Of the first description is one in my cabinet before alluded to, shaped somewhat like an air-balloon; the meshes are large and perfectly square. The pupa hangs in the centre, fixed by some few slight threads which diverge from it to all parts of the cocoon--so that it looks as if it was suspended in the air, like Mahomet's coffin, without support. Of the second description is a black one with very fine and nearly circular meshes: the threads that form these are thick, and seem to be agglutinated. In our own country, the cocoons of some beetles, as of _Hypera Arator_, _Galeruca Tanaceti_, and of some little _Tineæ_, also resemble gauze. Many of the larvæ, however, which spin these cocoons, whose thinness is probably attributable to the smallness of their stock of silk, seem anxious for a more complete concealment; and therefore commonly either hide them between leaves tied together, in some with a certain regularity, in others without art[527]; or thicken their texture, and render it opaque, by the addition of grains of earth[528], or of other materials with which their bodies supply them. These are principally of two kinds. The larvæ of _Lasiocampa Neustria_, _Arctia Salicis_, &c. after spinning their cocoons, cast from their anus three or four masses of a soft and paste-like matter, which they apply with their head all round the inside of the cavity; and which, drying in a short time, becomes a powder that effectually renders it opake. This is not, as might be conjectured, an excrement, but a true secretion, evidently intended for this very purpose: and, according to Reaumur, a similar powder, but white, derived from the varicose intestines, is used by the caterpillars of _Gastropacha quercifolia_, &c.[529] The other material, which is still more frequently employed, and which is occasionally mixed with the former, is the _hair_ which everyone has observed to cover so thickly the bodies of some caterpillars. This, after spinning a sufficient envelope, they tear, or in some instances cut off with their mandibles, and distribute all round them, pushing it with their head amongst the interstices of the silk, so as to make the whole of a regular thick texture. After this process, which leaves the body completely denuded, and often seems to give them great pain, they conclude by spinning another tissue of slight silk, in order to protect the forthcoming pupa from the surrounding prickly points. It should be observed, however, that though many hairy larvæ, as those of _Noctua Aceris_, _Arctia Caja_, and others, employ their hairs in the composition of their cocoons, the rule is not general, several never making any such use of them. Nor do all that do so employ them distribute them in the same manner as those above described, which rarely attempt to arrange them in any regular position. Reaumur has noticed a small hairy caterpillar that feeds on lichens, which is more methodical: this actually places its hairs upright, side by side, as regularly as the pales in a palisade, in an oval ring around its body, connecting them by a slight tissue of silk, which forces them to bend into a sort of roof at the top; and under this curiously-formed cocoon assumes its state of pupa[530]. Some larvæ make so much hair and so little silk enter into the composition of their cocoons, that on the first inspection they would be pronounced wholly composed of it[531]; others, thickening the interior of their cocoon with hair, line the whole with a viscid matter like varnish[532].

The larvæ of some saw-flies (_Tenthredo_ L.) are remarkable for inclosing themselves in a double cocoon, in which the inner is not, as in the silk-worm &c., connected with the outer, but perfectly distinct from it. Some species, as _T. Rosæ_ (_Cryptus_ Jur.), which have but a small stock of silk, compose the outer cocoon of thick silken cords crossing at right angles, and forming an oval net; which at the same time that it protects them effectually from the ants, which are always ready to attack them, demands much less silk than a covering of a closer texture. But the tender nymph itself requires to be inclosed in a case of a softer and more delicate substance; and accordingly the inner cocoon is composed of fine silk, woven so closely that the threads are scarcely perceptible under a microscope[533]. Reaumur mentions a hymenopterous larva belonging to Latreille's _Fossores_ (_Sphex_ L.) which thickened its cocoon with the legs, wings, and other relics of the flies which it had devoured[534]: trophies--like the drinking-cups of some savages, made of the skulls of their enemies, or the skull pyramid near Ispahan--of its powers of devastation.

It is a general rule, that those larvæ which spin cocoons, never in ordinary circumstances become pupæ without having thus inclosed themselves. An exception, however, is met with in the larva of a species of ant noticed by De Geer (_Formica fusca_ L.), some of the individuals of which inclose themselves in cocoons; while others neglect this precaution, and undergo their metamorphosis uncovered[535]. Rösel also made nearly the same observation on the larva of the flea[536].

I must say something with regard to the _situation_, often very remote from their place of feeding, in which larvæ fabricate their cocoons. A very considerable number, probably the majority, form them either partially (_Arctia lubricipeda_) or wholly under ground; others beneath dead leaves, moss, or in the chinks of the trees; others within the wood in substances on which they have fed; the larva of _Cossus_ leaves in these a communication with the open air by which the imago emerges; and a large number attach them to the leaves and branches of trees and plants; the cocoon of _Donacia fasciata_(?) is fastened by one side to the roots or surculi of _Typha latifolia_. There is usually nothing very remarkable in the mode of fixing them, the exterior threads being merely gummed irregularly to different portions of the objects which support them. But some effect this with greater art. I have one from New Holland, very long, which is suspended from a twig by a long riband, as it were, which entirely girths the twig. The larva of the magnificent silk-moth, _Attacus Paphia_, actually forms a solid silken stalk to its cocoon, an inch and half in length and a line in diameter, fastened by the other extremity to a twig, which it closely surrounds as if with a ring, at first sight resembling a fruit of a very singular appearance[537]. I have specimens of this cocoon with both stalk and ring. A bell-shaped cocoon fastened by a foot-stalk, but of softer consistence, to a blade of grass, found by Mr. Sheppard, I can also show you; and my friend Mr. Wilkin had a similar one out of the late Mr. Hudson's collection. Most larvæ spin their cocoons in solitude: some of those, however, which live in society do it close together under their common tent.

There are other cocoons that should be noticed here, such as those formed by the larva of _Zygæna Filipendulæ_, and some _Bombyces_, saw-flies (_Tenthredo_ L.), and beetles (_Curculio_, _Donacia_ F.), &c. These are formed of a substance which seems more analogous to gum than silk, yet furnished from the silk reservoirs, and usually present the appearance externally of parchment or membrane. That of the insect first mentioned is coated, however, with a slight interior silken lining; as indeed are almost all cocoons, of whatever substance.

* * * * *

The _second_ class, into which I have divided larvæ that inclose themselves in cocoons, includes those which form their coverings not solely or principally of silk, but in which other materials are mixed more or less. The cocoons of some of these larvæ are merely composed of a few leaves slightly tied together, either irregularly, or arranged, particularly when they are of a linear figure, with considerable symmetry. The grubs of many beetles, as of the rose-beetle, _Cetonia aurata_, &c., prepare themselves a cocoon, composed of earth, pieces of rotten wood, and any substances within their reach: which they fasten together with a glutinous secretion. The same material is employed by others in forming a cocoon wholly of earth; which is sometimes, as that of the stag-beetle, _Lucanus Cervus_, exceedingly hard; at others, as that of some moths, _Noctua ambigua_, &c, so slight as to fall to pieces as soon as touched[538]. Other cocoons are formed of grains of earth. Reaumur has given a very interesting account of the procedures of a larva in repairing one of these cocoons, from which he had broken off the top when just completed. Without quitting the interior of the walls that remained, it put out its head from the breach, and for more than an hour employed itself in selecting one by one grains of earth, which it conveyed with its mandibles and deposited within its case: it next spun all round the opening threads of silk, to which it attached grains of earth taken from the previously-stored heap, uniting them compactly by means of other silken threads. After employing three hours in this laborious process, the industrious little mason had reduced the diameter of the breach to a few lines. Reaumur was very curious to know how it would fill up this orifice, which would no longer admit the protrusion of its head outside the walls, as in its previous operations. He concluded, that while the rest of the cocoon was exteriorly formed of earth, this opening would be merely closed with silk. He was mistaken, however: the artist knew how to vary its manœuvres, and make its vault of one uniform texture. It spun across the opening a little net of silk, between the meshes of which it thrust grains of earth so dexterously that they projected as far as the outer surface, retained there probably by silken lines previously attached and fastened within. It then finished its habitation by fortifying the inside of the orifice with another layer of earth[539]. The ant-lion (_Myrmeleon_) spins a globular cocoon with its anus, which it covers with grains of sand[540]. One that I took in the forest of Fontainebleau, in the quarry that produces the crystallized sandstone called the _Fontainebleau fossil_, was covered with large and shining grains. Instead of the grains of earth or sand employed by these larvæ, those of another tribe substitute grains of stone detached from the softer walls, upon whose lichens they previously feed, which they unite into solid oval cocoons[541]. Those of a fourth form their cocoons of patches of short moss arranged with the roots downwards, and forming a vault, as it were, of verdant turf, admirably adapted for concealment[542]. The larvæ of some moths form their cocoons of irregular pieces of bark tied together with silk, and resembling when completed a knotty protuberance of the twig on which they are fixed. That of _Pyralis tuberculana_ constructs a pannier-shaped one of the parenchyma of the leaves of plants[543].

All these cocoons, however, must yield in point of singularity of construction, materials, and ingenuity, to one formed by a small caterpillar, described by the illustrious naturalist lately quoted, which feeds upon the oak. This cocoon is wholly composed of small rectangular strap-shaped pieces of the fine upper skin, or epidermis of the twig upon which it rests, regularly fastened to each other in a longitudinal direction with very slender silken cords. But the mode of its construction is even more remarkable than the substance of which it is fabricated. The caterpillar's first process is to form its slips of bark into two flat triangular wing-like pieces, projecting opposite to each other from each side of the twig, somewhat like the feathers of an arrow. It does not, perhaps, require any great degree of intelligence in a larva to give its cocoon the usual oval form, when it begins to arrange its materials in that shape from the very first, and round so good a mould as its own bent body; but we surely must admit that it is a task to which no stupid artist would be competent, to form first a multitude of strap-shaped laminæ into two triangular plates, and then to bend these plates into a case resembling the longitudinal section of a cone, with an elliptical and protuberant base,--the figure which the cocoon of this insect assumes. All the minutiæ of the manœuvres which it employs in this nice operation could not be comprehended without a more diffuse explanation than I have here room to give: suffice it to say, that the caterpillar fastens silken lines to each exterior opposite and longer side of the laminæ, and by applying all the weight of its body forces them to bend and approach each other, in which position it secures them by other shorter lines. It next repeats the same process with the upper and shorter sides of the plates; which when joined form the base of the cocoon. Both these tasks are accomplished in less than an hour, and the seams are so nicely joined as to be imperceptible. A fine inner tapestry of silk, covering all the asperities of the exterior walls, concludes its labours[544]. It is to be lamented that Reaumur was unacquainted with the moth that proceeds from the pupæ inclosed in these ingenious cocoons; which being small, and precisely of the same colour as the bark of the twig that supports them, are not to be discovered but by a very narrow inspection. It would seem, however, to be _Noctua Strigula_ of Berkhausen, _Pyralis strigulalis_ of Hubner[545]. The larva, he informs us, is found in May: its body is flatter than common, of a yellowish flesh-colour, clothed with tufts of red hair on each segment, and furnished with fourteen feet. Should this description enable you to detect it upon your oaks, a view of its ingenious procedures would amply repay you for the trouble of seeking for it. The larvæ of _Cerura vinula_, _Stauropus Fagi_, and several other moths, form their cocoons of grains of wood gnawed from the trees on which they feed. These grains they masticate, mixed with a glutinous fluid secreted from the mouth, into a paste, which forms a covering of an uniform smooth texture, and so hard as not readily to yield to a knife. Of a substance apparently nearly similar is composed the cocoon of a weevil related to _Liparus Pini_; which with its inhabitant was given me by the ingenious Mr. Bullock. A little moth, whose ravages have been before noticed[546], lines the interior of the grain of barley, of which it has devoured the contents, with silk; divides it into two apartments, into one of which it pushes the excrement it had voided, and in the other assumes the pupa[547].

These, and the other larvæ mentioned above, commonly form their cocoons of the substances I have indicated; but when by any cause they are prevented from access to them, they often substitute such other materials as are at hand. Reaumur fed a larva that formed its cocoon of minute fragments of paper, which with its mandibles it had cut from the piece that covered the glass vessel that contained it[548]: and the same circumstance happened to Bonnet.

Upon a former occasion I described to you the cases of various kinds formed and inhabited by the insects of the _Trichoptera_ Order (_Phryganea_ L.) commonly called case-worms[549]. As these serve for the pupa as well as the larva, they may be regarded as a kind of cocoon. I shall not repeat here what I then said; but having purchased from the collection of the late Mr. Francillon some that seem to belong to this or some cognate tribe, that are of a curious construction, I shall give you some account of two or three of them in this place. The first is not quite three inches long, of a sublanceolate shape, but rather widest towards one end. It consists of an internal tough and thick bag or cocoon, of a silk resembling fine wool of a dirty white colour, which is closely covered transversely by pieces of the stalk of a plant, about three-fourths of an inch in length, and crossing each other at an obtuse angle. The next is thicker and shorter: the internal bag is just covered with small fragments of wood like sawdust; over these are fastened irregularly, short stout pieces of a pithy stick or stalk, and the whole is clothed with a very close-woven ash-coloured web. It seems difficult to conceive how the inclosed animal could contrive to cover her habitation with this web without going wholly out of it. The third is the most curious and remarkable of all. It is nearly six inches long, and about four-fifths of an inch in diameter. It consists of a bag of thick cinereous silk web, to which are fastened, in a sextuple series, pieces of stick about an inch long, the end of one mostly resting upon the base of another: between each series a space of about three-tenths of an inch intervenes, but at the apex they all converge. This probably imitates the branch or stem of some tree or plant, in which the leaves are linear, and diverge but little from the stem. A label upon it states its country to be New Holland. I suspect the inhabitants of the two last cocoons to be terrestrial animals: the first is probably a true aquatic case-worm.

* * * * *

The same purpose for which the cocoons above described serve, is answered in the case of numerous _Dipterous_ insects, by a humble and less artificial contrivance--the skin, namely, of the larva; which, as was before observed[550], is never cast, but, when the insect is about to enter into the pupa state, assumes a different form and colour; becomes of a thicker and more rigid texture; and defends the included pupa, which is separate from it, till its exclusion. In this case the mouth of the larva is constantly different from that of the perfect insect, or at least has not with it those relations as to number and kind of organs, which have been observed in the mouth of other larvæ compared with the insects that they produce. The animal, immediately after it is clothed with this skin, if it is opened, exhibits only a soft gelatinous pulp, in the surface of which the exterior organs of the adult insect cannot yet be detected. Nature requires more time for their elaboration, or at least for the appearance of their outline, and to consolidate them. This pulp first takes an oblong form (_Boule allongée_ Reaum.), and afterwards that of the insect it is destined to give birth to[551]. The skin of the larva also serves for a cocoon to the pupæ of male _Cocci_[552]. The grub of the genus _Anthrenus_, so destructive to our cabinets of natural objects[553], when it assumes the pupa does not quit its skin, but only splits it open longitudinally on the back, and when it becomes an imago makes its exit through the orifice[554]. Some Lepidopterous larvæ even (_Alucita pentadactyla_, _Callimorpha rosea_, &c.) assume the pupa state within their last skin[555].

* * * * *

When a larva has finished its cocoon,--which with some species, that proceed so earnestly as though they had not a moment to lose, is the work of a few hours, of others about two or three days,--after a certain interval it casts its last skin, which is usually suffered to remain in the cocoon (but which one moth, _Geometra lacertinaria_, ejects through an opening purposely left in its bottom), and the pupa makes its appearance[556]. This interval is exceedingly various. Most larvæ assume the pupa state within a few days after they have formed their cocoons; but some not for several weeks, or even months. The caterpillar of _Bombyx cæruleocephala_, according to Rösel, lies three weeks in the cocoon before this change is effected; those of many _Pupivora_ and _Diplolepariæ_ Latr., according to Reaumur, six months[557]; that of _Phalæna urticata_ nine months[558]; and that of _Cimbex lutea_, according to De Geer, sometimes eighteen months[559]. Brahm observes, that such larvæ of the double-brooded moth, _Hepialus Testudo_, as form their cocoons in autumn, do not become pupæ until the following spring; while those which form them in summer undergo this change in a few days[560]. From this fact it might be conjectured, that the degree of heat prevailing at the time the insect incloses itself determines the period of the pupa's appearance; but this supposition seems contradicted by what Reaumur observed of a brood of the larvæ of _Phalæna urticata_, just mentioned, which, though they formed themselves cocoons in September, did not become pupæ till the June following[561]. I am unable, therefore, to assign any plausible cause for these extraordinary variations. The difficulty of comprehending how animals before so voracious can live so long without food may be partly surmounted, by adverting to the circumstance of its having attained its full growth, and laid up a store of nutriment for the development of the perfect insect. It is consequently no more wonderful that it should not have need of any further supply without casting off its upper integument, than that it should not eat after having done so and become a pupa.

FOOTNOTES:

[206] De Geer vii. 197.

[207] De Geer vii. 197.

[208] Ibid. 85.

[209] _Epist._ lxvii. 1694. 390.

[210] _Enum. Ins. Austr._ 575.

[211] _N. Dict. d'Hist. Nat._ i. 74.

[212] De Geer vii. 576.

[213] Ibid. 584.

[214] _Considerat. Géner._ 21. _Horæ Entomolog._ 353.

[215] De Geer, _Ibid._ Mr. W. MacLeay observes of the _Chilopoda_, or Centipedes, that they moult in the manner of _Crustacea. ubi supr._ 352.

[216] De Geer iii. 549. The figure of the forceps in De Geer (Ibid. _t._ xxv. _f._ 21) is not quite correct. The styles do not taper to a point, but are filiform and acute.

[217] Compare De Geer iii. _t._ xviii. _f._ 2 and 12. _q._

[218] See above, VOL. II. p. 401.

[219] PLATE XVI. FIG. 4. _c._ Reaum. v. _t._ xix. _f._ 16. De Geer _ubi supr._ _t._ xxxii. _f._ 26. According to Reaumur, the larva as well as the pupa of _Chermes Ficus_ has wing-cases (iii. 353).

[220] These are in the female sex of some _Coleoptera_, as _Lampyris_, &c. which retain in the perfect state nearly the same form which they had when larvæ. The larvæ of some _Staphylini_ are not very dissimilar in form to the perfect insect.

[221] The larvæ described in the first Section, which resemble the imago, are usually covered with a skin not materially different from that of the insect in that state.

[222] Huber _Fourmis._ 73; _N. Dict. d'Hist. Nat._ vi. 250.

[223] Reaum. v. 40. _t._ vi. _f._ 4-15.

[224] Müller, the Danish zoologist, relates, that he once met with a papilio which, with the true wings of the genus, had a head without antennæ or tongue, furnished with mandibles; and, in short, that of a true caterpillar. It was a female, which deposited eggs that proved barren. If this solitary instance was not a mistake, is it possible that some parasitic larva had devoured only the inclosed head of the butterfly, or so injured it that it could not reject the hard skin of the larva, and yet not be destroyed?

[225] The only larvæ which have a visible distinct neck are those of some _Dytisci_, _Staphylini_, and a few others, in which this part is quite distinct: proving the erroneousness of the opinion of those German entomologists, who consider the thorax as analogous to the neck of other animals, and hence call it _Halsschild_. In some lepidopterous larvæ, however, as in that of _Pieris Brassicæ_, though no visible neck presents itself, one is very perceptible when the insect stretches the head forward considerably. Reaum. i. 460.

[226] PLATE XVII. FIG. 13.

[227] Reaum. v. _t._ vi. _f._ 7. _i. c._

[228] In fact, in almost all Lepidopterous larvæ the head may be regarded as divided into two lobes or eye-shaped portions, which include in the angle formed by their recession anteriorly from each other, the nasus (_clypeus_ F.), the labrum, and other instruments of manducation. Posteriorly these lobes generally come into contact; but I have a specimen in which there is a narrow space between them.

[229] _Ins. Surinam._ _t._ xvii.

[230] _Ins. Surinam. t._ liii.

[231] _Ibid. t._ xxxii.

[232] _Ibid. t._ viii.

[233] _Ibid. t._ xxiii.

[234] _Ibid. t._ xiv.

[235] I purchased this singular caterpillar from the collection of the late Mr. Francillon, with his other exotic larvæ; but without any indication of the fly to which it belonged.

[236] De Geer vi. 352.

[237] De Geer iv. 66. ii. 922.

[238] De Geer v. 170.

[239] De Geer says, he could not make out the number of eyes of the larva of the whirlwig (_Gyrinus_): probably, as in that of _Dytiscus_, there are six. iv. 362. 385.

[240] Pez. 188.

[241] ii. 923, _t._ xxxvi. _f._ 1, _b b._ Fabr. _Philos. Ent._ 60.

[242] Lyonnet 41. _t._ ii. _f._ 1. c.

[243] De Geer vi. 307.

[244] Ibid, ii. _t._ xvi. Comp. _f._ 2 _a a_ with _f._ 14 _a a_.

[245] In the larva of _Cicindela_ there are _six_ palpi, as in the perfect insect.

[246] Lyonnet, _t._ i. _f._ 7. E. In the larva of _Callidium violaceum_, however, this part is of a singular shape, being orbicular. Kirby _Linn. Trans._ v. _t._ xii. _f._ 12. _a_.

[247] It is affirmed (_N. Dict. d'Hist. Nat._ vii. 333) that the larvæ of those _Coleoptera_ that live in carcases have mandibles almost membranous: those, however, of that of _Silpha rugosa_ are horny and hard.

[248] Lyonnet, _t._ ii. _f._ 1. D D, and _f._ 2, 3, 4.

[249] Kirby in _Linn. Trans._ v. _t._ xii. _f._ 7 _b._

[250] Cuvier _Anat. Comp._ iii. 322.

[251] Reaum. vi. 340.

[252] The larva of _Cicindela campestris_ has mandibles of this description. PLATE XVII. FIG. 13. _c´._

[253] See above, VOL. II. 275--.

[254] Reaum. v. 9. _t._ i. _f._ 4. _c c._ _l l._

[255] _Traité Anatom._ _t._ ii. _f._ 1. H H.

[256] Reaum. ii. _t._ 40. _f._ 4.

[257] De Geer v. 229.

[258] Ibid. iv. _t._ xi. _f._ 16. _p p._

[259] _Linn. Trans_. v. _t._ xii. _f._ 10.

[260] Cuvier _Anat. Comp._ iii. 323.

[261] De Geer iv. _t._ xv. _f._ 9. _b b._ The exterior and interior palpi are both represented in this figure.

[262] Reaum. vi. _t._ xxxvii. _f._ 5. _e e._

[263] Ibid. i. 125.

[264] PLATE XXI. FIG. 9. The organ with which the larvæ of _Hemerobius_, _Myrmeleon_, and _Hydrophilus_, spin their cocoons, is situated in the _anus_. The spinneret of the _Cossus_ is figured by Lyonnet _Anatom._ _t._ ii. _f._ 1. I. and _fig. 9_.

[265] De Geer vi. 370. This species (_Tipula Agarici seticornis_ De Geer) has two separate spinnerets. _t._ xx. _f._ 8. _m m._

[266] Lyonnet 55--.

[267] Reaum. iv. 166.

[268] Reaum. v. 155.

[269] Ibid. vi. _t._ xxxvii. _f._ 7. _b p._

[270] Ibid. _m e e_.

[271] Ibid. _f._ 6. _p._

[272] Ibid. Compare _f._ 4 with _f._ 6, 7.

[273] Ibid. _t._ xxxvi. _f._ 12. _s u e_.

[274] Ibid. _n e_, and xxxviii. _f._ 7, _d c._; De Geer ii. _t._ xix. _f._ 17. _d g._

[275] Reaum. vi. _t._ xxxvii. _f._ 4-6. 8.

[276] Ibid. _t_. xxxviii. First joint _f._ 8. _b f p._; jaws _f._ 7. _c d._; opening _o_, Ligula, _f._ 6. _l._

[277] De Geer ii. _f._ 17. Jaws _g g_; claw _d_; tooth _h_.

[278] Ibid. 674.

[279] Ibid. ii. 674.

[280] Reaum. iv. 376.

[281] _N. Dict. d'Hist. Nat._ xii. 64.

[282] _Anat. Comp._ iii. 322.

[283] At first in the _Dytisci_ they appear to have five joints; but, as I before observed, the first joint must be regarded as representing the maxilla.

[284] Lyonnet _Anatom._ 55, 58.

[285] De Geer v. 203.

[286] De Geer iv. 5. Legs of this kind are figured PLATE XXIII. FIG. 7.

[287] In the larva, however, of _Sialis_, or some kindred genus, in which, like those of _Scolopendra_, the prolegs are jointed, a pair distinguishes each abdominal segment. See Reaum. iv. _t._ xv. _f._ 1, 2. Compare De Geer ii. _t._ xxiii. _f._ 11.

[288] See above, VOL. II 286--.

[289] Ibid. 288.

[290] Lyonnet _Anatom._ _t._ iii. _f._ 8. _Coxa_ B. _Trochanter_ C. _Femur_ D. _Tibia_ E. _Tarsus_ F. _Claw_ G.

[291] De Geer iv. _t._ xiii. _f._ 20; and _t._ xv. _f._ 16.

[292] Ibid. ii. _t._ xvi. _f._ 5, 6, 7. _d e_: and _t._ xix. _f._ 4. _c f g h_.

[293] The larva of a scarce moth (_Stauropus Fagi_. See PLATE XIX. FIG. 4) is an exception to this. The first pair of its legs are of the ordinary stature, but the two next are remarkably long, and so thin and weak as to be unable to bear the body. Pezold. 119. Another minute caterpillar described by Reaumur has the third pair of the legs apparently fleshy and singularly incrassated at the apex into a pyriform figure, terminated by a pair of claws. This conformation is for some particular purpose in the economy of the animal, since they are the most busily employed of all in arranging the threads of her web. Reaum. ii. 258. In the larva of a geometer (_Geometra lunaria_) the third pair are remarkably long. Illig. _Mag._ 402. In that of another moth, according to Kuhn (_Naturf._ xvi. 78. _t._ iv. _f._ 3), the third pair of the fore-legs is remarkably incrassated, being twice as thick and long as the other pair, though consisting of the same number of joints, the last of which has claws.

[294] On the legs and prolegs see also what is said above, VOL. II. p. 286--.

[295] In some few instances these legs are dorsal. Ibid. 281.

[296] The claws or crotchets, though general, are not universal, in Lepidopterous larvæ. An exception is furnished to the rule by the singular _limaciform_ ones of _Hepialus Testudo_ and _Asellus_ of Fabricius, two moths forming Haworth's genus _Apoda_, which have no distinct prolegs, but in their stead a number of small transparent shining tubercles without claws. The larva also of one of the subcutaneous moths first discovered by De Geer in the leaves of the rose (i. 446), but whose history is fully given by Goeze, _Naturf._