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EN TOMOLOGY 
butterflies of a distasteful species before it becomes recognized 
as such, and that there exist in this region 2,000 individuals 
of species A and 10,000 of species B; then, if they are different 
in appearance, each will lose 1,200 individuals, but if they are 
deceptively alike, this loss will be divided among them in pro- 
portion to their numbers, and 4 will lose 200 and B 1,000. A 
accordingly saves 1,000, or 50 per cent. of the total number 
of individuals of the species, and B saves only 200, or 2 per 
cent. Thus, while the relative numbers of the two species are 
as I to 5, the relative advantage from their resemblance is as 
25 tOxT. 
If two or more distasteful species are equally numerous, 
their resemblance to one another brings nearly equal advan- 
tages. In cases of this kind 
and many are known—it is 
sometimes impossible to distinguish between model and mimic, 
as all the participants seem to have converged toward a com- 
mon protective appearance, through an interchange of features 
—the “ reciprocal mimicry ” of Dr. Dixey. 
From this explanation, the superior value of Mullerian as 
compared with Batesian mimicry is evident. 
The fourth condition—that the imitators differ from the 
bulk of their allies—holds true to such a degree that even the 
two sexes of the same species may differ extremely in colora- 
tion, owing to the fact that the female has assumed the like- 
ness of some other and protected species. The female of 
Papilio merope, indeed, occurs (as was just mentioned) under 
three varieties, which mimic respectively three entirely dissim- 
ilar species of Danainz, and none of the females are any- 
thing like their male in coloration (Frontispiece, Figs. 5-11). 
The specific identity of these four South African varieties of 
merope has been established by Trimen, Marshall and other 
investigators. 
The generally accepted explanation for these remarkable 
but numerous cases in which the female alone is mimetic, 1s 
that the female, burdened with eggs and consequently sluggish 
in flight and much exposed to attack, is benefited by imitating 
