184 THE MALAYAN PAPILIONIDE AS 
A, B,) has acquired exactly the same peculiarity of © 
having red spots instead of yellow. Lastly, in the © 
island of Timor, the female of P. Ginomaus (a species 
allied to P. Memnon) resembles so closely P. Liris 
(one of the Polydorus-group), that the two, which 
were often seen flying together, could only be distin- 
guished by a minute comparison after being captured. 
The last six cases of mimicry are especially instruc- 
tive, because they seem to indicate one of the pro- 
cesses by which dimorphic forms have been produced. 
When, as in these cases, one sex differs much. from 
the other, and varies greatly itself, it may happen 
that occasionally individual variations will occur having 
a distant resemblance to groups which are the objects 
of mimicry, and which it is therefore advantageous to 
resemble. Such a variety will have a better chance of 
preservation ; the individuals possessing it will be mul- 
tiplied ; and their accidental likeness to the favoured 
group will be rendered permanent by hereditary trans- 
mission, and, each successive variation which increases 
the resemblance being preserved, and all variations 
departing from the favoured type having less chance 
of preservation, there will in time result those singular 
cases of two or more isolated and fixed forms, bound 
together by that intimate relationship which consti- 
tutes them the sexes of a single species. The reason 
why the females are more subject to this kind of 
modification than the males is, probably, that their 
slower flight, when laden with eggs, and their exposure 
to attack while in the act of depositing their eggs 
