226 ENTOMOLOGY 



now often termed respectively Pierinse and Papilioninae. 

 Ithomiinse are mimicked also by Papilioninae and by moths of 

 the families Castniidae and Pericopidae. 



The discoveries of Bates in tropical South America were 

 paralleled and supported by those of Wallace in India and the 

 Malay Archipelago (where Danainse 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 Danainae are mimicked, each by a 

 distinct variety of the female of Papilio merope (Frontispiece, 

 Figs. 5-11). 



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 (Frontis- 

 piece, Figs, i, 4), 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 Muller's famous expla- 

 nation, 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 coun- 

 terfeiting the appearance of an inedible species; (2) that ob- 

 served 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 mimi- 

 cry 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 indi- 

 viduals. 



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



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



