CHAPTER I.

THE TRANSFORMATION.

Hanging to the slender branch of yonder rose-tree, swinging to and fro with the gentle air which blows in scented waves through the flower-garden, is a little object to which we wish to direct attention. Had not notice been thus directed to it, in all probability we should have passed it by, if we observed it at all, only considering it to be a broken twig or withered leaf suspended by a cob-web. We may examine it minutely, but all is quiet and motionless in the little mass, and it is impossible to detect the least sign of life. A casual eye would rest upon it without interest, and would turn away from it uninstructed as to its nature and properties. In colour it has nothing to attract--it is of a dirty white or brown, and in shape it is, though curious, so small, and so uninviting, that few would take the trouble to pay much attention to it. Day by day it swings from its silken cord, and is to all appearance an object without interest to all around it.

Yet this slumbering, unattractive mass contains a living being. Though the aspect of death has passed upon it, and though we may perhaps be unable to detect the symptoms of movement in its parts, it is yet alive, and the lapse of a little time will convert the slumbering being, thus singularly hung up to be the sport of the wind and rain, into a creature more extraordinarily active than perhaps any other in the animal creation. While it sleeps, great changes are taking place; it is receiving new organs, it is being matured, developed, perfected, fitted for a nobler existence, and for a higher range of duties, than it has yet known. Such is the _pupa_.

From these remarks it will be sufficiently evident that this chapter of our insect history has to speak of a period when there are but few traces of active existence in the insect, and it might therefore be supposed there remained little to be said upon a period of the insect's life which is only comparable to a prolonged sleep. But entomological science is too rich in interesting matters upon every subject to admit this conclusion, and we shall find that there is much to be narrated which equally, with what has formerly been written, is calculated to raise our admiration to the Great and Beneficent Author of all Nature.

If we turn to a Latin Dictionary and hunt out the word which stands at the head of this chapter, _Pupa_, we shall find several definitions of it given; for example, _a little girl_, _a doll_, and _a baby_. What have either of these to do with an insect? some will exclaim, and they may feel disposed to consider the great Linnæus, who gave the insect tribes while in this stage this title, to have been not over happy in his selection of terms. But those who thus exclaim have perhaps only seen _babies_ as they are clothed in England, possessing the power and comfort of free movement, and having their arms and legs at liberty. Between the aspect of these little creatures and our insects no one can trace any resemblance. But it is very different on the continent; there, out of the strange notion that it will keep the poor little being's limbs straight, it is the custom to wrap babies up in swaddling clothes, until they can neither stir hand nor foot, and they are made to resemble Egyptian mummies as nearly as possible. Babies wrapped up in this cruel and barbarous manner form objects of so peculiar an appearance, that it is quite ludicrous to trace the resemblance between them and the _pupæ_ of insects; and therefore Linnæus, as it appears, could scarcely have selected a better epithet for the insect than its present title of _pupa_, as it too has the aspect of being wrapped up in swaddling bands.

But, as we formerly mentioned with regard to larvæ, all insects in the _pupa_ state are not called popularly by their scientific and correct name. Those that are closely wrapped up, and are in fact complete mummy insects, are called sometimes by the term _Chrysalis_, or _Aurelia_, because they are sometimes of a _golden_ lustre, the one being derived from the Latin, the other from the Greek term for "gold," and this even when they are not gilded in this manner. Again, when, as we shall presently have to notice, the insect in the _pupa_ state is still capable of eating or moving, or when it does not lose its legs, its popular name is a _Nymph_. As in the preceding chapter, so in this, we shall not regard these terms, as they only create a great amount of confusion, but shall adopt the true term, _pupa_, throughout, whether the insect spoken of falls within the one or other of these popular divisions, or not.

We traced the larva in the last chapter up to that period in its history when it enters its cell, or otherwise retires to concealment, previous to its becoming transformed into the _pupa_. Here, immured in darkness, and alone, it is left to undergo that mysterious struggle of the vital powers which is to end in producing a new and more perfect creature out of one which, however perfectly adapted to its condition, is very far inferior, as regards the completion of its organization, to that which it is destined to become; and here we may appropriately pause to take up the history of the curious larva so recently described, at p. 207, as performing the feat of hanging itself up by the tail from cords spun by its mouth; since it exhibits to us in a striking point of view the shaking off of the old form of larva, and the putting on of the new one of pupa. In addition to this, it is, perhaps, one of the most astonishing instances of animal agility with which we are acquainted.

In order to make its manoeuvres and the difficulty of them the more easily comprehended, let us (to follow Messrs. Kirby and Spence in the same matter) put a case of a somewhat similar kind before the readers by way of supposition. Country fellows at wakes and fairs frequently--for the diversion of the company there assembled, or for a prize of some value in their estimation, perhaps a fat pig, or a leg of mutton--run races in sacks which are tied close about their necks, and of course tumble about a good deal, and display anything but a graceful mode of progression. "Now," say these authors, "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!"

Let us proceed to show in what manner the caterpillar performs this wondrous feat. After suspending itself in the way already described, a little time generally elapses, during which the insect by turns contracts itself, and then dilates again. At length its skin splits near its head, and a portion of the pupa appears, which acts like a wedge, and, being thrust partly through the slit, causes it to tear still higher and higher towards the tail. The insect continues its painful labours, swelling and contracting alternately, so as to push the torn skin higher and higher up, as one would roll off a stocking, until at length the old skin is folded into several rolls, and is quite at the tail. But the task is as yet only half accomplished; the most arduous and difficult part remains to be done. The pupa is shorter than the larva, and consequently hangs out of reach of the silken button in which the latter was firmly fixed by its hind legs. It seems now as if the poor insect must fall, for there appears no way for it to get up to the silk anchorage, and the folds of the pushed-up old skin are all that retain it in its position, which, as may be imagined, is far from a secure kind of fastening. How is it to disengage itself from 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 groundless; 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 manoeuvre: making its cast skin serve as a sort of ladder, it successively, with its 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. The tail is provided with a number of minute hooks which catch in the meshes of the silken button, and the pupa, thrusting it into the meshes of this button, feels quite secure as to the result, and drops safely into the perpendicular position, dangling in the air as gaily as did the larva before it. But its old skin still clings to it, and seems greatly to annoy it by its presence; so much so, that it sets about attempting to cast it down altogether. As it will be remembered that the legs of this skin are still firmly attached to the silk, in consequence of their hook-like form, it will be evident, that this also is a task of some arduousness. In order to get rid of it, it jerks itself about in various directions, and spins round very rapidly,--doubtless the reader has often seen the insect in this act, and has wondered what was its object in whirling round after this manner,--by this means at length the cast-skin appears loosed from its hold and drops off. The whole proceeding from first to last is represented in our engraving. The little hooks of the tail of the pupa are represented in the adjoining cut much enlarged. Well does Réaumur exclaim,--"These manoeuvres of withdrawing its tail from the old skin, of climbing up the old skin, and of hooking its tail in the silken button,"--and, as we might add, of whirling itself, and in other ways agitating itself to get rid of its old skin,--"are manoeuvres so delicate and perilous, that we cannot help wondering how an insect which only executes them once in its life, should execute them so well; and we are led to the inevitable conclusion that it has been thus taught by a Great and All-wise Master."

The manner in which other larvæ cast their skins and become pupæ when they enter their cell cannot be described, as they perform this act in all the privacy and darkness of their solitary habitations; but in all probability it differs in no respect from the manner in which the same creatures cast their skins when they moult, excepting that the new being which emerges from the cast-skin is no longer a larva, but a pupa.

The time occupied by the creature in its process of change differs in different species. In some it is short, in others it is long. Generally, it does not exceed a few days. We are told, however, of the larva of some insects which are six months before they become pupæ. The Baron de Geer tells us with surprise of the larva of a moth which he had watched. It became a larva, and spun its cocoon, in the month of August, 1746, and was attentively kept during the winter. The spring came, but the larva still remained a larva, and did not show any signs of changing its form; and winter came again, finding it still a larva: the second winter passed, and it was not until April 1748, that is, more than eighteen months after it first became a larva, and entered its cocoon, that it underwent the change, and became a pupa: some time afterwards it became a perfect insect.