MIMICRY. 



53 



resemblance in some of these cases is most extraordinary, 

 and no satisfactory explanation of the way in which it is 

 produced has been as yet advanced. In some cases the 

 resemblance is carried so far that the animal not only mimics 

 some natural object, but actually imitates what may be 

 termed the natural imperfections of the object. Thus, Mr 

 Wallace has described a -butterfly in which not only does 



Fig. 1 8.— Walking Leaf Insect {Phy Ilium). 



the under surface most closely resemble the leaf of a tree, 

 "but " we find representations of leaves in every stage of 

 decay, variously blotched, and mildewed, and pierced with 

 holes, and in many cases irregularly covered with powdery 

 black dots, gathered into patches and spots, so closely re- 

 sembling the various kinds of minute fungi that grow on 

 dead leaves, that it is impossible to avoid thinking at first 



