Chap. XIV.] ANALOGICAL RBSEMBLANGBS. 223 



fly belonging to a fourth genus. It deserves especial 

 notice that many of the mimicking forms of the Lep- 

 talis, 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 counterfeit- 

 ers have changed their dress and do not resemble their 

 nearest allies. 



We are next led to inquire what reason can be as- 

 signed for certain butterflies and moths so often assum- 

 ing the dress of another and quite distinct form; why, 

 to the perplexity of naturalists, has nature condescended 

 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 habitually escape de- 

 struction to a large extent, otherwise they could not 

 exist in such swarmsj and a large amount of evidence 

 has now been collected, showing that they are distaste- 

 ful 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 gen- 

 erations swarm over the whole country. Now if a 

 member of one of these persecuted and rare groups were 

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

 that it continually deceived the practised eyes of an 

 entomologist, it would often deceive predaceous birds 



