Evide7ices of Theory of N^atural Selection. 325 



modifications, expressly and exclusively adapted to 

 this end. For example what a remarkable series of 

 protective adjustments occurs in the life-history of the 

 Puss Moth — culminating with so comical an instance 

 of the particular device now under consideration as 

 the following. I quote the facts from Mr. E. B. 

 Poulton's admirable book on The Colours of Animals 

 (pp 269-271). 



The larva of the Puss Moth {Centra vinula) is very common 

 upon poplar and willow. The circular dome-like 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 colour strongly suggest 

 the appearance of little galls, or the results of some other injury 



Fig. hi. — The Inrva of Puss Moth {C.vitiitla) when undisturbed; 

 full-fed ; natural size. 



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

 the upper surface of the leaf, resembling the dark patches which 

 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 stiil occupied the whole surface of the body. 

 The latter gains a green ground-colour which harmonises with 

 the leaf, while the dark marking is chiefly confined 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, and usually rests on the 

 twigs of its food-plant (Fig. 1 1 1). The dark colour is still present 

 on the back but is softened to a purplish tint, which tends to be 

 replaced by a combination of white and green in many of the 

 largest larvae. Such a larva is well concealed by General Pio- 



