84 MIMICRY, AND OTHER PROTECTIVE 



possibility of their being found out by their enemies. 

 It is also very remarkable that in almost every case the 

 particular Ithomias and other species of Heliconida3 

 which they resemble, are noted as being very common 

 species, swarming in individuals, and found over a 

 wide range of country. This indicates antiquity and 

 permanence in the species, and is exactly the condition 

 most essential both to aid in the development of the 

 resemblance, and to increase its utility. 



But the Leptalides are not the only insects who have 

 prolonged their existence by imitating the great pro- 

 tected group of Heliconidse ; a genus of quite another 

 family of most lovely small American butterflies, the 

 Erycinidse, and three genera of diurnal moths, also 

 present species which often mimic the same dominant 

 forms, so that some, as Ithomia ilerdina of St. Paulo, 

 for instance, have flying with them a few individuals 

 of three widely different insects, which are yet dis- 

 guised with exactly the same form, colour, and mark- 

 ings, so as to be quite undistinguishable when upon the 

 wing. Again, the Heliconidse are not the only group 

 that are imitated, although they are the most frequent 

 models. The black and red group of South American 

 Papilios, and the handsome Erycinian genus Stalachtis, 

 have also a few who copy them ; but this fact offers no 

 difficulty, since these two groups are almost as domi- 

 nant as the Heliconidse. They both fly very slowly, 

 they are both conspicuously coloured, and they both 

 abound in individuals ; so that there is every reason to 

 believe that they possess a protection of a similar kind 



