CH. II] MIMICRY 9 



concerned, and the nature of the phenomenon may 

 perhaps best be made clear by a brief accomit of the 

 facts which led to the statement of the theory. 



In the middle of last centm-y the distinguished 

 naturalist, H. W. Bates, was engaged in making 

 collections in parts of the Amazon region. He paid 

 much attention to butterflies, in which group he 

 discovered a remarkably interesting phenomenon^. 

 Among the species which he took were a large number 

 belonging to the group Ithomiinae, small butterflies 

 of peculiar appearance with long slender bodies and 

 narrow wings bearing in most cases a conspicuous 

 pattern (cf. PI. X, fig. 7). When Bates came to 

 examine his catch more closely he discovered that 

 among the many Ithomiines were a few specimens 

 very like them in general shape, colour, and markings, 

 but differing in certain anatomical features by 

 which the Pierinae, or "whites," are separated from 

 other groups. Most Pierines are very different from 

 Ithomiines. It is the group to which our common 

 cabbage butterfly belongs and the ground colour is 

 generally white. The shaj)e of the body and also of the 

 wings is in general quite distinct from what it is in the 

 Ithomiines. Nevertheless in these particular districts 

 certain of the species of Pierines had departed widely 

 from what is usually regarded as their ancestral 

 pattern (PI. X, fig. 1) and had come to resemble very 

 closely the far more abundant Ithomiines among whom 

 they habitually flew (cf. PI. X, figs. 2 and 3). To 



1 Trans. Linn. Soc. vol. 23, 1862. 



