that I shall be correct in placing _P. Romulus_ as a third Indian form of the female _P. Pammon_, corresponding to _P. Melanides_, the third form of the Malayan _P. Theseus_. I may mention here that the females of this group have a superficial resemblance to the _Polydorus_ group, as shown by _P. Theseus_ having been considered to be the female of _P. Antiphus_, and by _P. Romulus_ being arranged next to _P. Hector_. There is no close affinity between these two groups of _Papilio_, and I am disposed to believe that we have here a case of mimicry, brought about by the same causes which Mr. Bates has so well explained in his account of Heliconidæ, and which thus led to the singular exuberance of polymorphic forms in this and allied groups of the genus _Papilio._ I shall have to devote a section of my paper to the consideration of this subject. The third example of polymorphism I have to bring forward is _Papilio Ormenus_, Guér., which is closely allied to the well-known _P. Erechtheus_, Don., of Australia. The most common form of the female also resembles that of _P. Erechtheus_; but a totally different-looking insect was found by myself in the Aru Islands, and figured by Mr. Hewitson under the name of _P. Onesimus_, which subsequent observation has convinced me is a second form of the female of _P. Ormenus_. Comparison of this with Boisduval’s description of _P. Amanga_, a specimen of which from New Guinea is in the Paris Museum, shows the latter to be a closely similar form; and two other specimens were obtained by myself, one in the island of Goram and the other in Waigiou, all evidently local modifications of the same form. In each of these localities males and ordinary females of _P. Ormenus_ were also found. 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,