90 



coloured central cloud ; others, again, entirely of a 

 pale or deep lead colour ; and all intermediate shades 

 occur : the number of spots also varies. (Stephens' 

 Illust. Brit. Lepid., vol. iv. p. 243.) 



The caterpillar {g, rather magnified) of this moth 

 is of an ashy white colour, with a brownish head, 

 and a number of small black spots, of which the 

 largest form a series on each side of the body. It 

 has sixteen feet, the three anterior pairs being arti- 

 culated, and attached to the three anterior segments. 

 The four following pairs are membranaceous, false, 

 ventral legs ; and the terminal pair anal, and also 

 membranaceous. They are below the middle size, 

 and the body is smooth. In regard to the predilec- 

 tion of this caterpillar for any particular kind of food, 

 only some kinds of apples were affected, which is the 

 more remarkable, because its principal food (whence 

 its specific name is derived) is the bird cherry, 

 although the white thorn is also even more subject to 

 its attacks ; whole hedges being sometimes entirely 

 defoliated in summer, and covered with webs. 



It is a peculiarity in the history of this insect, that 

 it is not only social in the caterpillar state (a), but 

 that it retains its sociality during the period of its 

 pupation (5), the cocoous being formed within the web 

 which had served for the abode of the caterpillars. 

 These webs are quitted from time to time, and new 

 encampments established at short distances from each 



