CHAP. XIV.] ANALOGICAL RESEMBLANCES. 353 



genera, equally close in their resemblance, may be found. Alto- 

 gether no less than ten genera are enumerated, which include 

 species that imitate other butterflies. The mockers and mocked 

 always inhabit the same region ; we never find an imitator living 

 remote from the form which it imitates. The mockers are almost 

 invariably rare insects; the mocked in almost every case abound 

 in swarms. In the same district in which a species of Leptalis 

 closely imitates an Ithomia, there are sometimes other Lepidoptera 

 mimicking the same Ithomia : so that in the same place, species 

 of three genera of butterflies and even a moth are found all 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 natural- 

 ists, 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 

 destruction to a large extent, otherwise they could not exist in 

 such swarms ; and a large amount of evidence has now been col- 

 lected, 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 and insects, and thus often escape 

 destruction. Mr. Bates may almost be said to have actually 

 witnessed the process by which the mimickers have come so closely 

 to resemble the mimicked ; for he found that some of the forms 

 of Leptalis which mimic so many other butterflies, varied in an 

 extreme degree. In one district several varieties occurred, and of 

 these one alone resembled to a certain extent, the common 

 Ithomia of the same district. In another district there were two 

 or three varieties, one of which was much commoner than the 



