Chap. XIV.] ANALOGICAL EESEMBLANCES. 223 



closely resembling a butterfly belonging to a fourth 

 genus. It deserves especial notice that many of the 

 mimicking forms of the Leptalis, as well as of the 

 mimicked forms, can be shown by a graduated series to 

 be merely varieties of the same species ; whilst others 

 are undoubtedly distinct species. But why, it may be 

 asked, are certain forms treated as the mimicked and 

 others as the mimickers ? Mr. Bates satisfactorily 

 answers this question, by showing that the form which 

 is imitated keeps the usual dress of the group to which 

 it belongs, whilst the counterfeiters have changed, their 

 dress and do not resemble their nearest allies. 



We are next led to inquire what reason can be 

 assigned for certain butterflies and moths so often 

 assuming the dress of another and quite distinct form ; 

 why, to the perplexity of naturalists, has nature con- 

 descended to the tricks of the stage ? Mr. Bates has, 

 no doubt, hit on the true explanation. The mocked 

 forms, which always abound in numbers, must habitu- 

 ally escape destruction to a large extent, otherwise they 

 could not exist in such swarms ; and a large amount of 

 evidence has now been collected, showing that they are 

 distasteful to birds and other insect-devouring animals. 

 The mocking forms, on the other hand, that inhabit the 

 same district, are comparatively rare, and belong to 

 rare groups ; hence they must suffer habitually from 

 some danger, for otherwise, from the number of eggs 

 laid by all butterflies, they would in three or four 

 generations swarm over the whole country. Now if a 

 member of one of these persecuted and rare groups were 

 to assume a dress so like that of a well-protected species 

 that it continually deceived the practised eyes of an 

 entomologist, it would often deceive predaceous birds 

 37 



