1 86 ENTOMOLOGY 



The discoveries of Bates in tropical South America were paralleled 

 and supported by those of Wallace in India and the Malay Archipelago 

 (where Danainae are the chief "models"), and of Trimen in South Africa 

 (where Acraeinae and Danainae serve as models). Trimen discovered a 

 most remarkable case, in which three species of Danais are mimicked, 

 each by a distinct variety of the female of Papilio cenea (merope) . 



So much for that kind of mimicry but how is the following kind to 

 be explained? The Ithomiinae of the Amazon valley have the same form 

 and coloration as the Heliconiinae, but the Ithomiinae themselves are 

 already highly protected. The answer is that this resemblance is of 

 advantage to both groups, as it minimizes their destruction by birds 

 these having to learn but one set of warning signals instead of two. This 

 is the essence of Miiller's famous explanation, which will presently be 

 stated with more precision. There are two kinds of mimicry, then: (i) the 

 kind described by Bates, in which an edible species obtains security by 

 counterfeiting the appearance of an inedible species; (2) that observed 

 by Bates and interpreted by Miiller, in which both species are inedible. 

 These two kinds are known respectively as Batesian and Miillerian 

 mimicry, though some writers prefer to limit the term mimicry to the 

 Batesian type. 



Wallace's Rules.; The chief conditions under which mimicry 

 occurs have been stated by Wallace as follows: 



" i. That the imitative species occur in the same area and occupy the 

 very same station as the imitated. 



"2. That the imitators are always the more defenceless. 



"3. That the imitators are always less numerous in individuals. 



" 4. That the imitators differ from the bulk of their allies. 



"5. That the imitation, however minute, is external and visible 

 only, never extending to internal characters or to such as do not affect 

 the external appearance." 



These rules relate chiefly to the Batesian form of mimicry and need 

 to be altered to apply to the Miillerian kind. 



The first criterion given by Wallace is evidently an essential one and 

 it is sustained by the facts. It is also true that mimic and model occur 

 usually at the same time of year; Marshall found many new instances 

 of this in South Africa. In some cases of mimicry, strange to say, the 

 precise model is unknown. * Thus some Nymphalidae diverge from their 

 relatives to mimic the Euplceinae, though no particular model has been 

 found. In such instances, as Scudder suggests, the prototype may 

 exist without having been found; may have become extinct; or the 



