Mimicry 59 



it, since the species would in any case be immune? In Eastern Brazil, 

 for instance, there are four butterflies, which bear a most confusing 

 resemblance to one another in colour, marking, and form of wing, 

 and all four are unpalatable to birds (Figs. 1—4). They belong to 

 four different genera and three sub-families, and we have to inquire : 

 Whence came this resemblance and what end does it serve? For a 

 long time no satisfactory answer could be found, but Fritz Miiller 1 , 

 seventeen years after Bates, offered a solution to the riddle, when 

 he pointed out that young birds could not have an instinctive 

 knowledge of the unpalatableness of the Ithomiines, but must learn by 

 experience which species were edible and which inedible. Tims each 

 young bird must have tasted at least one individual of each inedible 

 species and discovered its unpalatability, before it learnt to avoid, and 

 thus to spare the species. But if the four species resemble each other 

 very closely the bird will regard them all as of the same kind, and 

 avoid them all. Thus there developed a process of selection which 

 resulted in the survival of the Ithomiine-like individuals, and in so 

 great an increase of resemblance between the four species, that they 

 are difficult to distinguish one from another even in a collection. 

 The advantage for the four species, living side by side as they do e.g. 

 in Bahia, lies in the fact that only one individual from the mimicry- 

 ring ("inedible association") need be tasted by a young bird, instead 

 of at least four individuals, as would otherwise be the case. As the 

 number of young birds is great, this makes a considerable difference 

 in the ratio of elimination. The four Brazilian species are figured 

 on the accompanying plate (Figs. 1—4) : Lycorea halt a (Danainae), 

 Heliconius narcaea {eucrate) (Heliconinae), Melinaea ethra, and 

 Mcchanitis ly#im>u'a (Ithomiinae). 



These interesting mimicry-rings (trusts), which have much signi- 

 ficance for the theory, have been the subject of numerous and careful 

 investigations, and at least their essential features are now fully 

 established. Miiller took for granted, without making any investi- 

 gations, that young birds only learn by experience to distinguish 

 between different kinds of victims. But Lloyd Morgan's- experiments 

 with young birds proved that this is really the case, and at the same 

 time furnished an additional argument against the Lemarckian 

 principle. 



In addition to the mimicry-rings first observed in South America, 

 others have been described from Tropical India by Moore, and by 

 Poulton and Dixey from Africa, and we may expect to learn man\ 

 more interesting facts in this connection. Here again the preliminary 

 postulates of the theory are satisfied. And how much more that 

 would lead to the same conclusion might be added ! 



1 In Kosmos, 1879, p. 100. a Ilabit and Ituttivct, London, 1896. 



