Figs. 104, 105. — Chrysalides of the small Tortoise- shell Butterfly freeing themselves from the . 104, 105. — Chrysalides of the small Tortoi shell Butterfly freeing themselves from the Caterpillar skin.

the edges of the slit, and gradually pushes the old skin upwards. Thus the caterpillar skin ascends, its plaits are pushed nearer and nearer together, and it is soon reduced to a packet so small that it covers only the end of the tail of the chrysalis (Fig. 106).

But here comes the culminating point, the most difficult part of the operation. The chrysalis, which is shorter than the caterpillar, is at some distance from the silky network to which it must fix itself;

it is only supported by that extremity of the caterpillar's skin which had not been split open. It has neither legs nor arms, and yet it must free itself from this remaining part of the skin, and reach the threads to which it is to suspend itself

The supple and contractile segments of the chrysalis serve for the limbs which are wanting to it. Between two of these segments, as

Fie. 106. — Chrysalis of the small Tortoiseshell Butterfly completing the operation Fig. 107.— Chrysalis divested of the larva of casting its larval skin. skin.

with a pair of pincers, the insect seizes a portion of the folded skin, and with such a firm hold that it is able to support the whole of its body on it. It now curves its hinder parts slightly, and draws its tail entirely out of the sheath in which it was enclosed. It then reposes for an instant only, for it has not yet finished the laborious operation of its deliverance. It must free itself entirely from the dry skin which surrounds the extremity of its body.

The insect curves the part which is below its tail in such a manner that that part can embrace and seize the packet to which it holds on. It then gives to its body a violent shock, which makes it spin round many times on its tail, and that with great rapidity. During all these pirouettes the chrysalis acts against the skin; the hooks of its legs fray the threads, and break them or disentangle

themselves from them. Sometimes the threads do not break at once. Then the animal re-commences its revolutions in an opposite direction, and this time it is almost certain to succeed. Reaumur, however, saw a chrysalis which, after having tired itself in vain in its endeavours to get entirely free of its old skin, despairing of ever being able to , manage it, abandoned it where it was so solidly fixed. We represent ^-(Fig. 107), rather magnified, the chrysalis arrived at its final state, and suspended to a branch of a tree by a network of silk.*

We come now to the mode of suspension employed by those caterpillars, which, after having fixed themselves by the tail, strengthen the support by means of a small silk cord passed round their body.

It is again to Reaumur, that indefatigable observer of the habits of insects, that we go for the details of this manner of suspension.

According to Re'aumur, these caterpillars make and put on this belt in three different ways. But of these three ways the simplest, and the least liable to meet with accident, is that employed by the larva of the Cabbage Butterfly {Fieris brassicce). When the time for its metamorphosis is only a few days distant, one may observe this caterpillar engaged in stretching threads on different parts of the case in which it is confined. It then chooses a spot, which it covers entirely with threads, some more compact than the others, and disposed in layers, which cross each other in different directions. These threads form a thin white cloth, against which the belly of the caterpillar and later that of the chrysalis are applied. Very soon we see a small hillock of silk rising. The caterpillar hooks itself on to this by the claws of its hinder feet, and sets to work to secure itself

To understand this process, it suffices to know that after having lengthened its body to a certain point, this caterpillar can turn back its head on to its back, and reach to the fifth ring, having its three pairs of true legs in the air. But without putting the caterpillar into such an unnatural position, let us take it in a position in which it is simply bent sideways in such a manner that its head, with the thread-spinning apparatus, which is below, can be applied opposite and pretty near to one of the legs belonging to the first pair of membranous legs. Our caterpillar begins by fixing on this point a thread, which is the first of those that are intended to tie it up securely. " This thread," says the illustrious author of "Memoires pour servir h. I'Histoire des Insectes," " must pass over the caterpillar's body,

It has been remarked that only those whose continuance in the pupal state is short, undergo their metamorphosis in this apparently inconvenient position. — Ed.

iqo THE INSECT WORLD.

and be attached by its other end near the leg corresponding to that near which the first end was fastened. To spin the thread the proper length, and at the same time to fix it in its proper place, the caterpillar has only to bring round its head to the fifth segment. The thread will be drawn ft-om the spinning apparatus as the head advances over half the circumference of the circle which it has to describe \ and when it has described this, there will only

Fig. io8.— Caterpillars of the Cabbage Butterfly {Pietis brassiccr).

remain for it to secure the second end of the thread agamst the support. Thus the head, which was at first placed against one of the legs, advances little by little on the outline of the fifth ring as far as to its middle (Fig. io8). It is the facility the caterpillar has of reversing its body that enables it to make its head perform this journey; in proportion as it moves it over the circumference of the; ring, it twists its body. And at last, when it has brought it over the top of the segment, its body is exactly folded in two; it draws it. litde by little from this situation by bending towards the other side, | and by causing its head to pass gently over the last quarter of the! circle. At last the. caterpillar finds itself bound on the second side;; the head rests on the thread-covered plane, and the insect fixes the! second end of the thread."

It has only to repeat the same manoeuvre as many times as there

Fig. io8.— Caterpillars of the Cabbage Butterfly {Pietis brassiccr).

are threads wanted to make a strong band. But each thread embraces the head, or rather the lower part of the head, for it knows how to make each thread it spins ghde into the bend or crease of its neck by a Uttle movement of its head. It must disengage its head from under the band, not a difficult operation. It Fig. 109. — Caterpillar of the Pieris brassicse. causes it to slide along the threads near one of the places where they are fixed, and it is then in the position indicated by the foregoing engraving (Fig. 109).

About thirty hours after the caterpillars have succeeded in making themselves fast, they have completed their transformation into chrysalides. In Fig. no the chrysalis of the above-mentioned caterpillar is seen in two different positions, and held by the same band which first supported the caterpillar. Those caterpillars which construct cocoons make them of^silk and other substances. These cocoons are, for the most part, oval or elliptical, sometimes boat-shaped, and ordinarily white, yellow, or brown in colour. The threads may very slightly adhere together, or be closely united by a gummy substance with which the caterpillar lines the interior of the cocoon, and which it expels from the anus. Some cocoons are composed of a double.envelope, others are_ of a uniform texture. Some are of a tissue so close that they entirely hide the chrysalis ■ contained within; others form a very light covering, through which the chrysalis can be easily perceived (Fig. III). Among caterpillars that make a very slight cocoon, some, as the Caiocalas (Fig. 112), gather two or three leaves into a ball, to protect them. Others strengthen their cocoons, and render them Pupae o/rferisFig. no.brassicse. opaque by adding earth or other substances, often obtained from their own bodies. Some, after having spun their cocoon, cast forth through the anus three or four masses of a matter

Fig. 109. — Caterpillar of the Pieris brassicse.

Among caterpillars that make a very slight cocoon, some, as the Caiocalas (Fig. 112), gather two or three leaves into a ball, to protect them. Others strengthen their cocoons, and render them Pupae o/rferis brassicse. Fig. no. opaque by adding earth or other substances, often obtained from their own bodies. Some, after having spun their cocoon, cast forth through the anus three or four masses of a matter /rferis br Fig. no.

resembling paste, which they apply with their head to the inside of the cocoon, and which, drying quickly, becomes pulverulent Others employ for the same purpose the hairs with which their bodies are covered. The larva of Acronyda aceris (Figs. 113-115) is covered with tufts of yellow hair. Reaumur made these caterpillars work under his eye in glass vases. They make the layer which is to form the exterior surface of their shell, or cocoon, of pure silk, and when it is thick enough, tear out their hair, now from one place, now from another. But we will leave the illustrious observer to relate this operation himself, which must without doubt be

Fig. III. painful to the poor animal:— Cocoon, after Reaumur, ''Its two jaws are the pincers the caterpillar uses in seizing a portion of one or other of the tufts of hair; and when it has seized it, it tears it out without much

Fig. 113.— Larva of Acronycta aceris.

difficulty. It at once places this against the tissue it has already commenced, in which it entangles it at first simply by pressure; it

LEPIDOPTERA.

fixes it then more securely by spinning over it. It does not leave off tearing out its hairs till it has entirely stripped them off. When the caterpillar has taken between its jaws and torn out a whole tuft of hair, the head carries it and deposits it on some part of the lower surface of the cocoon; but it does not leave the hairs of such a large parcel together. The next moment one sees its head moving about very quickly; then taking a portion of the hairs ■from the little heap, it distributes them about on the neighbouring parts of the cocoon. If one opens one of these shells before the caterpillar has become a chrysalis, the larva, which is quite naked, and which was only known by its hair, can be no longer recognised."

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