140 



ORGANIC EVOLUTION 



behavior of the caterpillar of the puss moth : " The larva 

 of the puss moth (Centra vinula) is very common upon pop- 

 lar and willow. The circular domelike eggs are laid either 

 singly or in little groups of two or three, upon the upper 

 side of the leaf, and being of a reddish color strongly suggest 

 the appearance of little galls or the results of some other in- 

 jury. The youngest larvae are black, and also rest upon the 

 upper surface of the leaf, resembling the dark patches which 



FIG. 40. Caterpillar of the large elephant hawk-moth (Ch&rocampa elpenor). [After WEIS- 



MANN and POULTON.] 



a. In normal position when feeding, b. In " terrifying attitude." Compare Plate 79, Fig. A, 

 which shows the same caterpillar in natural colors. 



are commonly seen in this position. As the larva grows, the 

 apparent black patch would cover too large a space, and 

 would lead to detection if it still occupied the whole surface 

 of the body. The latter gains a green ground-color which 

 harmonizes with the leaf, while the dark mark is chiefly con- 

 fined to the back. As growth proceeds the relative amount 

 of green increases, and the dark mark is thus prevented from 

 attaining a size which would render it too conspicuous. In 

 the last stage of growth the green larva becomes very large, 



