TRUE MIMICRY 93 



which must make it easier for the birds to recognize them as 

 uneatable. Everything which marks out these unpalatable morsels, 

 and makes them more readily recognizable, must be to their advan- 

 tage, and therefore must have been favoured by natural selection 

 (PI. II, Fig. 13). 



In the same way, every increase of resemblance on the part of the 

 mimics would increase their chances of escaping notice, and any one 

 who is accustomed to observe butterflies in nature can well under- 

 stand that even very slight resemblances may have formed the 

 beginning of the selection process ; perhaps even a mere variation in the 

 manner of flight, combined with the habit of associating with the 

 swarms of Heliconiidse. I myself have many times been momentarily 

 deceived in our own woods by a White of unusually majestic flight, so 

 that I took it for an Apatura or a Limenitis. If, therefore, individual 

 Whites occurred here and there in the Amazon valley, which flew 

 somewhat after the manner of the Heliconiidag, and associated with 

 them, they might possibly have attained a certain degree of security 

 through that alone, and it would be greatly increased if at the same 

 time they varied somewhat in colour in the direction of their 

 companions. 



In any ease there can be no doubt whatever that in these cases 

 a real transformation of the species in colour and marking, and 

 perhaps often, too, in form of wing, has taken place, and that within 

 comparatively modern times — let us say during the distribution of a 

 species which required protection over a large continent, or since the 

 last breaking up of an immune species into local species. Various 

 facts prove this ; above all, the circumstance that it is often only the 

 females which exhibit this protective mimicry ; and that one and the 

 same species may mimic a different immune species in different areas, 

 but always the one occurring abundantly in that area, and so on. 



Definite examples will make this clearer, and I will only say in 

 a.dvance that, since the discovery of Bates, numerous cases of mimicry 

 in butterflies have been found, not only in South America, but in all 

 tropical countries which have a rich Lepidopteran fauna. And it is 

 not only between the Heliconiidse and the Pieridse that such relations 

 have been evolved; many much-persecuted, unprotected species of 

 different families everywhere mimic species which are rejected on 

 account of their nauseous taste, and these, too, belonging to different 

 faimilies. The Heliconiidse are a purely American group, but in the 

 Old World and in Australia their place is taken by the three great 

 families of Danaides, Euploeides, and Acrseides, since, as it seems, they 

 all taste unpleasantly, and are rejected by all, or at least by most, of 



