THE YOUNG INSECT 19 



internal ligaments that hold the membranes together. 

 We may illustrate this fairly correctly by blowing out a 

 kid glove — though the glove, of course, has no connective 

 threads within to prevent it assuming the balloon shape. 

 The butterfly remains hanging from the empty chrysalis 

 case until its wings are sufficiently hardened for Might. 

 Then it soars away into the sunlight — an exquisite being, 

 differing in a thousand ways from its caterpillar form. 



The changes which mark the growth of an insect from 

 the egg to the adult are termed its " metamorphosis." 

 When these changes are gradual and not very distinct, as 

 in the case of the cockroach, the insect is said to undergo 

 incomplete metamorphosis, and the word " nymph " is often 

 used to describe its immature state. But when the stages 

 of growth are strongly marked, as in the case of a butterfly, 

 the metamorphosis is said to be complete, while the insect 

 is known first as a larva or caterpillar, then as a pupa or 

 chrysalis, ere it becomes adult. 



Metamorphosis is by no means confined to insects. 

 We may witness the phenomenon, at least to a limited 

 extent, in the development of all animals, although strictly 

 speaking the term is used only to describe those form- 

 changes which follow birth or hatching. When a chick 

 breaks through the egg-shell, it has already lived for many 

 days ; and for its nourishment during this period of early 

 development the yolk is provided. In almost all such 

 cases — i.e. w r hen ample yolk provision is made for pre- 

 birth development — the young animal is born or hatched 

 in a form closely resembling that of its parents. The 

 form-changes which take place as it grows to maturity 

 are so slight that w r e can scarcely speak of them as a 

 metamorphosis. But vast numbers of animals, especially 

 in the sea, lay eggs which are meagrely provisioned with 

 yolk, and hatching takes place, of necessity, at a very 



