270 THE COLOUES OF ANIMALS 



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 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 con- 



FlG. 59.— The larva of Puss Moth (C. vivula) when undisturbed ; 

 full-fed ; natural size. 



spicuous. In the last stage of growth the green larva 

 becomes very large, and usually rests on the twigs of 

 its food-plant (see fig. 59). 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 Protective 

 Eesemblance, and one may search a long time before 

 finding it, although assured of its presence from the 

 stripped branches of the food-plant and the faeces on 

 the ground beneath. 



