Evidences of Theory of Natural 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 (Cerura viniula) 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 
: | 0 
i 0 |} o fe 
- iy | rt a oe 
Fic. 111.—The larva of Puss Moth (C. wula) when undisturbed; 
full-fed ; natural size. 
to the leaf. The youngest larvee 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 biack 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-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. 111). 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 larvee. Such a larva is well concealed by General Pro- 
