226 ENTOMOLOGY 
now often termed respectively Pierinze and Papilionine. 
Ithomiinze are mimicked also by Papilioninze and by moths of 
the families Castniidee and Pericopidee. 
The discoveries of Bates in tropical South America were 
paralleled and supported by those of Wallace in India and the 
Malay Archipelago (where Danainz are the chief “ models”’), 
and of Trimen in South Africa (where Acrzeinz and Danainze 
serve as models). Trimen discovered a most remarkable case, 
in which three species of Danainz are mimicked, each by a 
distinct variety of the female of Papilio merope (Frontispiece, 
Figs. 5—I1). 
So much for that kind of mimicry—but how is the following 
kind to be explained? The Ithomiinz of the Amazon valley 
have the same form and coloration as the Heliconiinz (Frontis- 
piece, Figs. 1, 4), but the Ithomiinz 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: (1) 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 Muller, in which both 
species are inedible. These two kinds are known respectively 
as Batesian and Mullerian 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: 
“1. 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, 1s external and 
