So far there is no evidence that these
light-coloured insects are not females of a distinct species, the males
of which have not been discovered. But two facts have convinced me this
is not the case. At Dorey, in New Guinea, where males and ordinary
females closely allied to P. Ormenus occur (but which seem to me worthy
of being separated as a distinct species), I found one of these
light-coloured females closely followed in her flight by three males,
exactly in the same manner as occurs (and, I believe, occurs only) with
the sexes of the same species. After watching them a considerable time,
I captured the whole of them, and became satisfied that I had discovered
the true relations of this anomalous form. The next year I had
corroborative proof of the correctness of this opinion 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 confirmative of
the supposition that both forms of female are of one species; and when
we consider, further, 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, sufficiently
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 supposed to exhibit
one of the intermediate steps in that process, which has been
accidentally preserved in company with it