Here it hangs, head downwards, awaiting the coming events. The splitting and casting of the skin goes on just as in the case of the Large White, but there is this puzzle to be solved: how can the insect shuffle itself out of its old coat without falling to the ground, leaving the cast-off garments still hanging by the hooks of the claspers? This really seems a matter of impossibility, since the little hooks which alone suspend the insect are thrown off with the skin of the claspers.
The thing is managed in this way. As the skin slowly splits through the wrigglings of the apparently uncomfortable occupant, it is gradually pushed backward—that is, upward—till it is in a shrivelled condition, and the body of the insect is nearly free. But the chrysalis thus brought to light is provided with little hooks on the end of its 'tail' by which it can attach itself to the irregularities of the crumpled coat. Its conical abdomen is also very flexible, and it can, by bending this, seize hold of a ridge in the skin, holding it between the segments. Thus, although practically quite free from the old garb, it never falls to the ground.
There is now, however, another point to be attended to. The newly formed chrysalis desires to be entirely independent of its cast-off skin, and to suspend itself directly from the silky carpet it has prepared. To this end it works steadily for a time, alternately bending its supple abdomen from side to side, gripping the folds of the skin between the segments, pulling its body a little higher at each movement, and securing itself at each step by the little hooks at its extremity.
So it climbs, and at last it reaches the network of silk fibres, and thrusts the tip of its abdomen among them till some of the hooks have taken hold. Not satisfied with this, it turns its body round and round to get the little hooks so entangled between the silk fibres that a fall is impossible, and in so doing it frequently pushes the old skin out of its place so that it falls to the ground.
Although the caterpillars of this species do not show any great gregarious tendency when nearly full fed, yet it is not an uncommon thing to find several hanging from the under surface of one leaf, all being attached to the one common carpet at which all had worked. And when bred in confinement, a number will often spin in company in a corner of their cage. I have thus obtained a cluster of thirty-seven pupæ, all hanging by the 'tails' to the same mass of silk, which was so small that they formed quite a compact mass of beings with their tails close together.
Fig. 28.—The Cocoon of the Emperor Moth.