152 THE MALAYAN PAPILIONIDE AS 
by the discovery in the island of Batchian of a new 
species allied to P. Ormenus, all the females of which, 
either seen or captured by me, were of one form, and 
much more closely resembling the abnormal light- 
coloured females of P. Ormenus and P. Pandion than 
the ordinary specimens of that sex. Every naturalist 
will, I think, agree that this is strongly confrmative 
of the supposition that both forms of female are of 
one species; and when we consider, farther, that in 
four separate islands, in each of which I resided for 
several months, the two forms of female were obtained 
and only one form of male ever seen, and that about 
the same time, M. Montrouzier in Woodlark Island, 
at the other extremity of New Guinea (where he 
resided several years, and must have obtained all the 
large Lepidoptera of the island), obtained females 
closely resembling mine, which, in despair at finding 
no appropriate partners for them, he mates with a 
widely different species—it becomes, I think, suffi- 
ciently evident this is another case of polymorphism 
of the same nature as those already pointed out in 
P. Pammon and P. Memnon. This species, however, 
is not only dimorphic, but trimorphic; for, in the 
island of Waigiou, I obtained a third female quite 
distinct from either of the others, and in some degree 
intermediate between the ordinary female and the 
male. The specimen is particularly interesting to 
those who believe, with Mr. Darwin, that extreme 
difference of the sexes has been gradually produced 
by what he terms sexual selection, since it may be 
