CHAPTER V.

THE GREAT CHANGE.

We must now spend a short time in narrating the particular circumstances which attend this interesting event,--the extrication of the insect from its pupa case. We shall, in the first place, speak of such pupæ as are not aquatic, and, afterwards, of the singular ones which are so. In the case of the butterfly, which, as we have recommended repeatedly its being nursed and bred, it will be expedient to mention first, the extrication of the insect is, comparatively with some others, a very simple operation. The insect within is seen to struggle for a time, twisting its body in various ways, until at length a longitudinal slit appears down the middle of its thorax. The slit extends gradually along the head, and down the parts which compose the breast, until the insect emerges from the outer case. The inner membranes are now to be removed, and this, after a little time, is fairly accomplished, and the butterfly emerges, and, leaving the pupa skin behind it, by-and-by plunges for the first time upon the soft waves of the summer air. This is one of the simplest of these methods of extrication.

A very natural difficulty will arise in the mind as to what possible means of escape can be granted to such insects as live in the pupa state in the interior of old trunks of trees, or even in little caves of the earth. These cases have all been satisfactorily provided for, puzzling as they may seem. Take, for instance, the pupa of the great goat-moth, the _Cossus ligniperda_, of which we give a representation here. This creature lies buried in a deep excavation, formerly made by itself when in the larva form, inside the trunk of a willow. How is it to get back to the hole at which it entered? Without legs, without any other apparatus by which it might drag itself forward, one would say it is in a hopeless case; it must lie there and perish, for there appears no way of extricating it from its den. But not so. Helpless as it appears, it will certainly make its way out, and taste the sweets of liberty, and be wafted along the fields of air. But how? Let us suppose a man in such a condition; let his feet be bandaged together, so that they cannot move; let a strait-jacket be put upon his body, and secure his arms and hands; after this, let a leathern bag be put over his head, and tied down round his middle; then put him in a cellar, and bid him work his way out and up the stairs until he reached the front door, where he must undo his bandages, and slip himself out of his strait-jacket and hood; after which, he may go wherever he likes. What a feeling of despair would fill the poor prisoner's mind, promised his release on condition that he should accomplish it in that way! To him it would be a task altogether impossible, even though his life were offered as the reward of his success. It is not less a question of life and death to the insect than it might be to him; yet its extrication is accomplished, not only in a very simple, but in a very easy manner.

If the reader will carefully examine the representation of the insect given in the last page he will notice that the pupa case is provided with certain sharp points, which are all directed towards the tail of the insect; these sharp points are called by entomologists _adminicula_. They are of infinite consequence to the insect. Who has not himself performed, or been the subject of, the trick of causing a grain of barley to creep up the sleeve? The manner in which it is gradually pushed up is strikingly similar to that in which the pupa of the _cossus_ is forced upwards and out of its wooden gallery. It will be readily supposed that, in consequence of the peculiar direction assumed by the tooth-like processes in question, it will be very difficult to push the pupa backwards, as the points would catch in any obstacle and arrest its progress in that direction; but they offer no resistance to its moving in a forward direction. The manner in which the insect proceeds, then, is as follows:--Being capable of slightly shortening and lengthening the lower part of its body, which is the part thus provided with hooks, it begins to push backwards, but the hooks catch in the sides of the wood, and thus prevent it from moving back, and it is, consequently, actually driven forwards; and so it continues to thrust itself gradually forwards in this simple manner, just as a boy with his hands tied might thrust himself forwards as he lay on the ground, by pushing against any object with his feet. In this way the patient creature moves, we may be sure, by very slow degrees; but that matters little; it moves until it has at length reached the opening of its gallery outside the tree, where it may often be seen sticking out half way. Here, by a remarkable instinct, it ceases to move forwards, for it would otherwise tumble down, and probably destroy itself. At length, after violent struggles, its swathing bands are all either torn asunder, or slidden off, and the insect wings its way in unrestrained freedom far from the scene of its triumphs of patience and hope. The pupa of the "father long-legs" makes its way up from the subterranean chamber in which it has so long been sheltered, fed, and protected, and reaches at length the surface of the ground, where it becomes the perfect insect.

But other pupæ, although not, perhaps, quite so arduously placed as in the last instance, nevertheless present us with an extremely difficult puzzle, as to how the included insect is to be extricated from its swathing bands. The common flesh-fly, or blow-fly, for instance, in the pupa state is shut up in a membranous case, out of which there seems no escape; but there is a way, and the manner in which the insect gets out of its prison is a remarkably curious one, well repaying the trouble of a little close observation. At the larger end, under which the head of the fly lies, and from which it always issues, there is commonly a sort of lid which can be pushed off like the lid of a box, and the insect can then walk out at pleasure. But in the case of the pupa of the blow-fly this lid is not very easily removed, and the fly, therefore, is furnished with a most ingenious method of thrusting it off. On opening the larger end of such a pupa, if the fly within is ready to come out, a most curious phenomenon will be seen. The insect moves towards the lid, and there begins to blow out its head in the most extraordinary manner, swelling it to twice its natural size; a moment after it will resume its natural size; then again it will puff it out, making its two eyes to start asunder, and its head to assume several different shapes in succession! Two representations are annexed of the striking figure of the insect's head when it thus causes it to swell out. After repeating this action several times, the fly emerges from the pupa. The cause of this remarkable dilatation is the filling of a membrane, situated at the middle part of the head, with air, by which it is blown out into a sort of bladder as large as the head itself. This acts as a kind of lever, and eventually pushes up the lid of the pupa case, allowing the insect to make its exit unmolested. This part generally disappears afterwards, and the head becomes alike firm and unyielding in all its parts; but it may, in at least its rudiments, be seen even in the head of the adult fly, by slightly pressing its head between the fingers, when it appears as at _x_ in the cut.

More singular still are the circumstances which mark the exit of the insect from the pupa case in other instances; and yet more strikingly than those narrated, do they exhibit to us the amazing exercise of the Divine attributes of wisdom and forethought in the case of these humble beings. The larva of a species of moth, which dwells in a wooden cell scooped out of the poplar tree, to which there is no door by which it can escape readily, gnaws away the wood until it leaves only an extremely delicate layer between it and the outside of the tree, which is as thin as writing paper. This done, it enters into the pupa state. Its time in that condition being accomplished, it moves itself by the same contrivance as the _cossus_, and actually pushes through the thin layer, and appears on the outside of the tree, thus making its escape from prison by pushing down a part of its prison wall!

An instance described by the naturalist Bonnet is yet more ingenious in the arrangements by which the insect escapes. While in the larva form it takes up its abode inside the leaf of an ash, curiously rolled up into a cone; and then, after a time, it becomes a pupa, forming a silken cocoon of a very slight texture, and, therefore, easily ruptured by the insect, which it suspends like a hammock in the midst of its habitation. It is the closely joined sides of its leafy dwelling that form a barrier which, were it not for the precaution of the larva, would be impenetrable to so small and weak an animal. But, like the last-mentioned, this larva seems to be aware of the feebleness of its next condition, and gnaws in the leaf a round opening, taking care not to cut through the exterior thin layer of tissue, or _epidermis_. This door is to serve the insect for its exit in due time. But in proportion to its bulk, its green chamber is of considerable size. How, then, shall the insect know the exact place where its portal is situated? How, without a clue, shall it discover in its dark abode the precise circle which requires only a push to throw open its gate? Even this is foreseen and provided for. Out of all other positions in which the little hammock, of which we spoke, might have been hung, and they are numerous, the larva has been directed so to place it, that the silken cord which suspends the head is fastened close to the side of the door which it has previously constructed; and the insect, when it emerges from the pupa, guided by this thread, like Theseus, makes its way out of an apartment which, but for this contrivance, might have been to it a labyrinth as inextricable as that of Minos. Other insects adopt the same precaution of gnawing a doorway for the escape of the perfect insect, only leaving a sufficient thickness of outside tissue to protect the helpless pupa within from the invasion of enemies from without.

Upon the pear or willow tree may sometimes be found an illustration of escape from the pupa, altogether well deserving our notice. In such situations the brown flask-shaped cocoon of the emperor moth may occasionally be discovered. In structure it is composed of a solid tissue of layers of silk, almost of the texture of parchment; but at the narrow end, or that which may be compared to the neck of the flask, it is composed of a series of loosely attached longitudinal threads, converging like so many bristles to a blunt point, in the middle of which is a circular opening, through which the moth makes its escape, the threads readily yielding to pressure from within, and acting somewhat on the principle of the wires of the opening to a rat-trap, or the willow cricks of an eel-trap. The silk of its cocoon is of so strong a texture, and so closely gummed, that had both ends been similarly closed, the egress of the insect would have been impracticable. But, it may be thought, such a cocoon is exposed to the attacks of a number of insect enemies, who might easily find entrance to it at the opening thus left at one of its ends. This source of peril has been foreseen. Within the exterior funnel-shaped end, at some little distance down, the insect has constructed a second funnel composed of a similar circle of needle-pointed threads, which, proceeding from the sides of the cocoon, converge to a point, and form a cone through which not the smallest aperture is left. From the arched structure of this singular dome, and from the fact just mentioned, that no visible opening can be discerned in it from without, it is rendered quite impenetrable to the most violent attacks of besiegers, while it yields to the slightest pressure from within, and allows the insect to emerge from its cocoon with the utmost facility. When it has passed through it, the elastic threads resume their former position, and the empty cocoon presents just the same appearance that it did before. A celebrated naturalist (Rösel), was sorely perplexed at this, the first time he had the gratification of watching the insect escape. He states that he could scarcely help thinking that there was something supernatural in the appearance of one of these fine emperor moths in a box in which he had put a cocoon of this kind; but in which he could not discover the slightest appearance of any insect having escaped from it, until he slit it longitudinally, and then found it to be empty!

Mr. Rennie mentions an instance, perhaps not so ingenious, but equally curious, with this history of the proceedings of the emperor moth, in a little insect, also a moth, which also dwells upon the willow. It spins an elastic shroud for its pupa, of the singular shape of a boat with the keel uppermost. Its first step is to spin two walls of whitish silk of the required form; and when these are completed, it draws them forcibly together with elastic threads, so placed as to retain them closely shut. The passage of the moth out of this cocoon might have struck Rösel with still greater surprise than he had felt at witnessing that of the emperor moth; for in that cocoon there was at least no apparent difficulty to prevent the egress of the insect, as the opening existed in it at one end, whereas in this there is no opening at all. The insect escapes at the joining of the sides, the threads giving way in a particular spot; and the sides, though originally requiring force to draw them together into the requisite form, become so elastic as to close again when the moth has passed between them, and made its escape. The cocoon preserves precisely the same form after the insect has quitted it as before, and it is impossible, by the naked eye, to detect the place of its exit.

As a general rule, insects make their escape from the pupa case head foremost; but there occurs a very singular exception in the case of some of the gall insects. The males of these insects contrive to make their escape out of the pupa case, formed of the dried skin, tail foremost; and as they thus back out of their dwelling, their wings are necessarily turned backwards over their heads; but a little exercise soon puts the ruffled insect in proper plume again, and the wings resume their customary position.

Some curiosity may be felt to know in what way the silk-worm moth escapes from the double prison,--the pupa case, and the cocoon,--in which she is concealed. How is the moth to make its way through the dense mass of fibres all glued together, which walls her in on every side? Her delicate wings and body would never endure anything like the severity of the struggle necessary to enable her to force her way through this, to her, solid and resisting mass. Though much attention has been paid to the transformations of this particular insect, it is somewhat curious that it is still a matter on which opinions are divided, as to how the insect succeeds in making its egress. Some suppose that the eyes, which are the only hard organs of the head, are the instruments by which the threads are divided, their numerous minute facets serving the purpose of a file. Others hold the belief that the insect pours out a fluid which acts upon the gum and silken fibres of one end of the cocoon, and so softens them that they easily give way to the slightest pressure from within. "Perhaps the two opinions," observe Messrs. Kirby and Spence, "may be reconciled by supposing the silk-worm first to moisten, and then to break, the threads of the cocoon. In those that are of a slighter texture, a mere push against the moistened end is probably sufficient; and hence we find in so many newly-disclosed moths the hair in that part wet and closely pressed down."

It has been supposed, in cases where the cocoon is a hard, almost wooden cell, that the feeble insect prisoner within is provided with a peculiar chemical fluid, of greater powers of solution than are requisite in the last instance. The cocoon of the "pussmoth," in particular, is so hard and dense, as to resist even the point of a penknife; and the insect it holds confined within it is a weak creature, totally unprovided with any apparatus fit for penetrating walls so hard and dense as these. What is it to do? "Here," observe the writers last quoted, "the eyes are clearly incompetent; nor could any ordinary fluid assist their operations, for the gum which unites the woody particles of the cocoon is indissoluble in _aqueous_ menstrua. What an aqueous solvent cannot effect, an _acid_ is competent to; and with a bag of such acid our moth is furnished. The contents of this she pours out as soon as she has forced her head through the skin of the pupa, and upon the opposite end of the cocoon. The acid instantly acts upon the gum, loosens the cohesion of the grains of wood, and a very gentle effort suffices to break down what was, a minute ago, a strong barrier. How admirable and effectual a provision! But there is yet another marvel connected with it. Ask a chemist of what materials a vessel ought to be to contain so potent an acid; he will reply,--Of _glass_.[O] Yet our moth has no glass recipient; her bottle is a membranous bag; but of so wonderful a fabric as not to be acted upon by a menstruum, which a gum, apparently of a resinous nature, is unable to resist! This fact can only be explained by the analogous insensibility of the stomach to the gastric juice, which can dissolve bone; and it is equally worthy of admiration. In both cases, the _vitality_ of the membranous or fleshy receptacle secures it from the action of the included fluid; but _how_, who shall explain?"

The naturalist, Huber, the patient historian of the ants, gives us a very interesting account of the proceedings of these wonderful insects, in actually _assisting_ the young out of their silken cases. These pupæ are enclosed in a tissue of silk, of so compact a texture, and formed of so strong a silk, as to render it impossible for the prisoner within to rupture the fibres, and get out of prison. The worker ants, therefore, are instructed by a heavenly Ruler and Guide to give help to the prisoners, and to secure their egress. But how do these indefatigable attendants ascertain precisely the moment when their aid is required? The insect within has no power of voice to cry out for help, nor those without, in all probability, the faculty of hearing, if it could do so. It seems probable that they are acquainted with it from some slight movements which take place within, which they ascertain by means of their antennæ. Whatever it be, the attendants never interfere at a wrong time. Their manner of proceeding is beautifully described in the following words of this author:--"Several males and females lay in their envelopes in one of the largest cavities of my glazed ant-hill. The labourer-ants assembled together, and appeared to be in continual motion around them. I noticed three or four mounted upon one of these cocoons, endeavouring to open it with their teeth, at that extremity answering to the head of the pupa. They began to thin it by tearing away some threads of silk where they wished to pierce it, and at length by dint of pinching and biting this tissue, so extremely difficult to break, they formed in it a vast number of apertures. They afterwards attempted to enlarge these openings, by tearing or drawing away the silk; but these efforts proving ineffectual, they passed one of their mandibles into the cocoon, through the apertures they had formed, and by cutting each a thread, one after the other, with great patience, at length effected a passage, of a line[P] in diameter, in the superior part of the web. They now uncovered the head and feet of the prisoner, to which they were desirous of giving liberty; but, before they could effect its release, it was absolutely necessary to enlarge the opening. For this purpose these guardians cut out a portion in the longitudinal direction of the cocoon, with their teeth alone, employing these instruments as we are in the habit of employing a pair of scissors. To expedite the work some raised up a little slip cut out in the length of the cocoon, whilst others drew the insect gently from its imprisonment. When the ant was extricated from its enveloping membrane, it was not, like other insects, capable of enjoying its freedom, and taking flight; it could neither fly, nor walk, nor without difficulty stand, for the body was still confined by another membrane, from which it could not by its own exertions disengage itself.

"In this fresh embarrassment the labourer-ants did not forsake it: they removed the satin-like pellicle which embraced every part of the body, drew the antennæ gently from their investment; then disengaged the feet and the wings, and lastly, the body, with the abdomen and its peduncle. The insect was now in a condition to walk, and receive nourishment, for which it appeared there was urgent need; the first attention, therefore, paid it by the guardians was that of giving it the food I had placed within their reach."

It is droll to add, and it may be some of our readers may feel somewhat abashed at the fact, that these labourer-ants are extremely particular in the observance of great order and regularity in their chambers; and they therefore carefully sweep up all the cast-off coverings, which are collected together, and deposited in one of the most distant lodges of their habitation. Could man, with all the powers of reason, and the faculties of an immortal being, have evinced a more striking instance of careful, gentle, and patient assistance in the hour of need than we see manifested in the case of these insects? Alas! how often does man need to come to them to learn not only a lesson of wisdom and order, but of the tenderest sympathy and affection. How often lies a poor fellow-creature in the bondage of hopeless poverty, or in the embarrassment of inextricable difficulties! How seldom does his emergency meet with that resolute and thorough-minded earnestness of brotherly love, which will patiently give him help and pity, until his troubles are surmounted, and his steps set free!

It is time that we spoke somewhat upon the extrication of insects from their pupa cases, even when under water. Here arises a great difficulty;--the wings of the insects thus placed, if wet with water, would be unfitted for flight, and would probably frequently lead to the death of the insect by drowning. Yet it is to leave its sub-aqueous abode, mount up through the waves overhead, and finally emerge without a drop of water clinging to its body, and from the glassy surface of the water it is to take its flight into the air. Some will be tempted to exclaim,--"This is a clear impossibility!" Far from it. The little worm so well known to anglers as the "caddis-worm," performs this feat with the greatest ease, and in the following manner:--

It has been mentioned that the larva known under this name constructs for itself a case of various materials in which it dwells at the bottom of the waters, where the hand of the young angler knows well to find them. This case is heavier than water, and consequently cannot float, and so carry the insect to the surface. As the insect enters the pupa state it weaves, at the entrance of its singular habitation, a grating of silk, which, strange to say, is not only not softened and melted away by the water, but hardens under it until it is as hard as gum. This little grating is of a circular form, and fits exactly into the opening, and is perforated with holes, so as to look something like the gratings which cover our coal-cellar mouths in the pavement of cities. These holes are for the purpose of letting in fresh water for the respiration of the insect. Out of this under-water cell the insect must make its escape. To enable it so to do the pupa is furnished with two strong curved jaws, which are of no other use than to assist it in making an opening in one of the silken doors of its case, as they are cast off immediately afterwards, and there remains not a vestige of them in the perfect insect. This opening made, the pupa forces its way out at that end. But what then? How is it to reach the surface, even now? Its legs, as will be seen by looking at the cut, are furnished with a number of hair-like processes, which assist it in swimming; it therefore, still enclosed in the waterproof coat--the pupa skin--strikes upwards to the surface, and reaching it, its skin splits, its impervious raiment is cast aside, and the insect springs from the surface into the air without the minutest drop of water to impede her flight, or injure the delicate tissue of her wings!

We may take another common insect for an illustration of this mode of escape from the pupa, of an equally interesting kind. If the reader will on some fine summer day resort to any place of standing water by the road-side, he may probably succeed in discovering the emergence of a number of _gnats_; and a very amusing occupation it is to stand by and watch the insect,--this moment an occupant of the waters, and the next darting in the air, a new and air-breathing form of existence! About ten days after the gnat has become pupa, it prepares for leaving that state and becoming a perfect insect by raising itself to the surface of the water, stretching out its body there, the thorax, or, in simpler language, the front enlarged part being raised above it. Immediately the eye of the observer detects the fact that some change is taking place in the insect; the enlarged portion cracks and splits, and through this opening the head of the gnat makes its appearance; then the trunk of the insect rises in a curious manner through the breach, and more and more of its body rises, preserving all the time a perpendicular position, so that it looks just as if it were rising out of the water, and not out of the horizontal pupa case floating on the surface. The upright body of the gnat now resembles a mast in a boat, only that it is continually being raised higher and higher by the gradual emergence of the insect. Its wings and legs are all folded closely down its sides as is shown in the cut; and it has therefore no power at all to prevent its being overset by a breeze, and drowned in the little waves below; the lower portion of its body alone retains it in this position, being as yet contained within the pupa case. No ship-builder dare venture to put a mast of such proportions into any of his vessels, for fear of their being top-heavy, and hence liable to heel over in a gale of wind. And undoubtedly many gnats, particularly in windy weather, are shipwrecked as soon as they emerge. This is, in fact, a moment of peculiar danger to the little insect-mariner, and a breath of untoward air will frequently drive it about like a ship in a tempestuous ocean; and if it is once laid on its side, all is over with the gnat; no patent apparatus can save it; and we have the mournful testimony of Réaumur, that in stormy weather he has seen a vast number of such shipwrecks in the mimic ocean of a pool of water. Generally speaking, the peril is only momentary, and the insect emerges in safety. Having thus raised itself to the perpendicular position, the gnat withdraws its two forelegs from the pupa case, and stretches them out; then it draws out its two next; and now feeling safe, it quits the perpendicular position and bends toward the water, plants its feet on its glistening surface, which is to it as safe as the land, since it has the faculty of walking on the waves. It is now in perfect safety, its wings expand and become dry, and presently the insect will for the first time make use of them by flying to some adjoining twig.

But we need not in many cases leave our homes to see an escape from the pupa in every respect as singular as the last, and in many, precisely identical. Before the writer's study-window was an artificial fountain, in which, as the water was not constantly allowed to play, aquatic insects of various kinds had permission to establish themselves. Nor were they long in availing themselves of this liberty. A week or two of genial summer weather was sufficient to people the water with various inhabitants among them was a little creature which will be recognised by every reader when we mention its title--"the blood-worm." It is in reality not a worm at all, although resembling worm in shape, and in its serpent-like movements. This little creature was for a time particularly active; and in a tumbler of water taken from the fountain might be seen perhaps a dozen of them twisting about in a very singular manner. By-and-by a change came over them, and it turned out that the worm-like creatures had become pupæ of a blackish colour, thus at once deciding their insect character. They belong, in fact, to the insect called the _Chironomus plumosus_. These black pupæ were scarcely less active than the red blood-worms, or larvæ of the same insect. They flapped about their tails with great vehemence, and thus, although their bodies naturally sink in the water, they were able to swim from the bottom to the surface, or from side to side. Observing that they had finished their appointed period in the pupa form, we became anxious to watch their change into the perfect insect. Neglecting, however, to notice them at the proper period,--the afternoon of a warm sunny day, we were astonished the next morning to find a surprising number of pupa skins lying empty of their tenants on the surface, as though some of the water fairies enumerated in fable had been dancing on the waves all night, and left their little black shoes behind them in their haste to flee from the light of the smiling morning. We determined to be better prepared for the observation on that day; and as the afternoon came we had the gratification of seeing a large number of these insects rise from the water, all in the following[Q] manner:--They rose up from the bottom and reached the surface by the peculiar movement of their tails just described; there the thorax was thrust above the water, and immediately the insect burst its cerements, elevated itself by a wave-like motion from the rest of the pupa-case, which filled with air, and now glistened like silver; it then planted its forelegs on the water, withdrew the rest of its body from the case, unfolded its wings, and in a few moments was sailing in the thin air. On one stormy day the surface of our fountain was bestrewn with the dead and dying bodies of these insects drowned in the waves.

De Geer,[R] speaking of the pupæ of a moth, states, that he was not fortunate enough to witness the manner in which they quit their watery abode. But he seems to think that they quit the pupa case, then mount to the surface of the water, or up some aquatic plant, in order to reach a dry spot, where they remain, their wings being developed afterwards, and that thus the risk of their being wetted is avoided. Their bodies being lighter than the water, he conceives, accounts for their being able to rise to its surface. Too much weight, however, must not be attached to this observation, as it is not accompanied with satisfactory ocular evidence of the fact.

The pupa of the "dragon-fly" furnishes us with a very interesting example of escape; and it well deserves the reader's attention, if he be so placed as to have the opportunity of observing it. Perhaps, indeed, few insects afford us such a singular series of interesting facts as are to be found in the escape of this one from its pupa. The best method of observing their change is to procure as many of the larvæ as possible, to put them in a basin of water, at the bottom of which are a quantity of dead leaves, and to allow several sticks to be in the water touching the bottom of the basin, and reaching above the level of the water, as shown in the cut. Then we must watch carefully to notice any of the larvæ which, having become pupæ, creep towards the edge of the water. These are such as will in all probability be the first to undergo the change, for they come to that position in order that they may get dry before proceeding further. If these are now closely observed, they will be seen after the lapse of a little time to leave their position, and to begin creeping about in search of a suitable spot where they may undergo their metamorphosis. Most probably they will select for this purpose the sticks we have introduced into the basin, and, after running up and down them, will fix upon a particular spot, where they place themselves securely, the head invariably uppermost. From what will be subsequently mentioned, it is necessary that the insect should fasten itself so firmly to the branch, that not even a violent effort would disturb its position. This is secured by the insect thrusting the sharp claws with which its feet are armed into the stem on which it rests. The points of these claws are so fine and hard as even to penetrate wood with facility. They are shown in the cut; and even after the dragon-fly has escaped out of the pupa case, they may be easily made to fasten upon a piece of a branch, by simply pressing the feet against it very lightly. In order to watch the changes of this insect Réaumur once, whilst staying in the country, collected a large number of the pupæ, and placed them on a piece of cotton-print tapestry, where they soon felt at home, and fixed themselves in preparation for their change, without moving far from the spot where they had been placed. At few periods of the day could a visit be paid to the room where this tapestry was hung without seeing a spectacle at once diverting and extraordinary. Previous to its changes the pupa becomes more transparent, and the large and beautiful eyes of the insect it encloses grow increasingly brilliant. These signs always indicate that the transformation is nigh at hand.

It comes to pass in the following manner:--Some movements of a struggling kind take place inside the pupa case; and at length the case splits at the upper part, near the head: through this rent the body of the dragon-fly appears and tears it open, acting like a wedge, until the slit extends along the head across to the two eyes. The latter transverse slit is produced by a contrivance similar to that mentioned in the case of the blow-fly, a sort of air bladder which the insect distends at its pleasure, and thus causes the skin covering its head and eyes to split open. The head and body of the insect rise and make their appearance through the slit; and the head is now so much larger than it appeared while in the pupa case, that it seems almost impossible that it could ever have been contained within it. The insect continues to rise perpendicularly out of the case, and the legs make their exit, leaving the leg cases of the pupa undisturbed in their attachment to the support on which it rests. In order to facilitate the disengagement of the rest of its body the insect now bends itself in a curved form backwards, being only kept from falling by the last rings or segments of its body being still embraced by the sheath of the pupa case. When it has extricated itself thus far, it begins to move about its legs in different directions for several minutes, as if to get them into use; but after this it ceases all movement whatever. Not a quiver can be seen in its limbs, and the young observer would be inclined to conclude,--as a great entomologist once did, the first time he witnessed the changes of this insect,--that it was in reality dead, and that it was a waste of time to watch it any longer. This state of profound inaction may endure for a quarter, or even half an hour: it appears to be intended in order to give time to the insect to recruit its strength for a fresh and more violent series of efforts, and to admit of its parts becoming hardened and dry. Suddenly, as we are, perhaps, carelessly looking on the inanimate object, it performs a feat of the most surprising, because unexpected agility. Its body, which was previously much bent backwards, is now swung forwards and bent into a curve; it then swings back, and then forwards again, and so quickly that it almost seems to leap. It then rests its legs upon the front part of the pupa case, and pulls the rest of its body out of the case by degrees, and then creeps forward, leaving the pupa case behind, still immovably fixed upon the plant.

"Behold," says Réaumur, "the dragon-fly new born, but very different from those which traverse the air, or rest upon the plants around. It is quite in disguise. The body, though longer than the pupa case out of which it was drawn, has not got all its natural length. The wings, which are the large and useful organs of these flies, have as yet very little more volume than they had when enclosed in the short and straitened pupa case. They are merely furrowed plates, or laminæ, of some thickness, and arranged one over the other, as if packed together. One can scarcely conceive how each of these wings can acquire its proper dimensions,--how it is to enlarge and lengthen sufficiently. They are folded into plaits like a fan, or like the leaf of a tree just about to be developed; hence they naturally appear very narrow, and the cause of their appearing so short is, that each of their longitudinal portions is folded up like the paper lanterns, more frequently used by nuns than by other persons."

The remaining portion of the dragon-fly's history will be found in the next chapter.[S]

Some curious instances are given by various authors of the escape of more than one insect from the same pupa. Thus we are told that a male and female emperor moth were once produced from one larva, and therefore one pupa, of extraordinary size. Messrs. Kirby and Spence tell us of a German entomologist who says, that two specimens of the pine-lappet moth were once produced from one pupa, which was of the remarkable size of two inches in length and one in thickness. But these are very rare instances, the common and almost universal rule being that one pupa only contains one insect.

Nothing now remains for us to add to the insect's history in the pupa state. Already,--for it is Spring far advanced,--the air is becoming peopled with insect tribes--

"The insect youth are on the wing, Eager to taste the honied spring, And float amid the liquid noon."

A thousand times ten thousand, nay, thousands of thousands, are already in the air; and the low hum of their wings may be heard if we stand breathless and listen in the midst of some sequestered spot, far from the roar and bustle and strife of town life. But the great life-season of the insect world is yet to come; and though May whispers it is nigh, June, July, and August must bring it to us, and with it a teeming multitude of insect flutterers more numerous than the stars of heaven, or the sand-grains of the sea-shore.