242 ANIMAL LIFE 



slung up by a silken hammock to a wall or a bent. 

 The play of light and shadow is reflected in its colours, 

 and the play of more profound and active agencies 

 than these is remoulding within it the body of the 

 caterpillar into that delicately poised organism the 

 butterfly. 



The lifedfistory of the common cabbage-white 

 butterfly will give point and example to these state- 

 ments. The minute, vase-like, exquisitely sculptured 

 eggs are laid by the female on the cabbage leaves or 

 Other cruciferous plants. In the course of a week 

 the young caterpillar emerges. Its worm-like body 

 is composed of a head, thorax, and abdomen. The 

 head carries powerful jaws inserted between the upper 

 and nether lips, rudiments of antennae, and a few simple 

 eyes. The thorax consists of three segments, each of 

 which carries a pair of stumpy legs. The abdomen, 

 divided into nine segments, possesses clasping feet on 

 the last four of them. The colour is a whitish tinge 

 speckled with grey, and from the third thoracic seg- 

 ment to the last abdominal one, paired black marks 

 indicate the breathing holes or spiracles. Movement 

 consists of a series of muscular waves passing from 

 behind forwards, aided by strides of the fore- and 

 hind-feet. 



The first decisive act of the young larva is to cast 

 its skin. A crack appears along its back, and the 

 moult is done by peeling off the skin inside out. There 

 is now room for expansion, and this the caterpillar 

 seeks to fill first with its own husk and then with the 



