The larva, although now fresh and smart in its appearance, is exhausted by these struggles and its prolonged fast. The new skin, moreover, is very soft and tender, even to the cases of the head and legs, which are normally very hard. But a short period of rest suffices to dry its skin and sharpen its appetite, and then it eats more vigorously than ever. We will now leave the caterpillar for a moment while we look at its cast-off clothes. They are still clinging to a stem so firmly that they can scarcely be removed without injury. The hard shell that covered the head and jaws is perfect in form, and so are the claws and cases of the legs. All the hairs or spines that happened to adorn the previous owner still retain their positions; and the whole skin, although always more or less shrivelled, is sometimes so slightly altered in form that it might be mistaken for a living caterpillar if not closely examined. But this is not all. For, according to the accounts of some authoritative observers, the lining of the digestive organs, which is really a continuation of the outer skin, is cast off (or rather cast _out_) at the same time, as are also the linings of the larger breathing tubes which are presently to be described. We have seen that some caterpillars, on quitting their egg cases (which may really be regarded as the first moult), make their first meal of the old covering. So also some of them, in their future moultings, exhibit an apparently useless economy (seeing that they are surrounded by an abundance of their natural vegetable diet) by devouring their old coats! In the face of this fact we can hardly describe them as strict vegetarians. [Illustration: FIG. 16.--THE CATERPILLAR OF THE PURPLE EMPEROR BUTTERFLY.] Having thus passed through its first hardship, the caterpillar has by no means seen the end of the troubles and dangers that beset it; for, during its existence in the larval state, it has to go through a series of three, four, five, or even six moults, all of which are periods of considerable inconvenience, and perhaps even pain, and frequently prove fatal. And it is by no means an uncommon thing to meet with the lifeless body of an unfortunate individual who, as shown by its shabby appearance and the silken carpet under its feet, has evidently fallen a victim to the dangerous process of ridding itself of an old garment. But this is only one of the many dangers to which caterpillars are exposed. Throughout every hour of the day the sharp and hungry eyes of the numerous insect-eating birds are searching the leaves for such delicacies to satisfy the wants of themselves and their broods. The lively little lizards, too, during the sunny hours are busily engaged in searching them out among the foliage of heaths and banks.