2. ORNITHOPTERA POSEIDON, Doubleday. _O. Poseidon_, Db. Ann. of Nat. Hist. xvi. p. 173; Westwood, Cat. of Orient. Ent. pl. 11, 14. The numerous specimens of _Ornithoptera_ which I obtained in various parts of New Guinea and the adjacent islands show so much instability of form, colouring, and even of neuration, no two individuals being exactly alike, that I am obliged to include them all in one variable species, to which I believe must also be referred _O. Pronomus_, G. R. Gray, from Cape York, _O. Euphorion_, G. R. Gray, from North Australia, _O. Archideus_, G. R. Gray (ex Boisd.), erroneously said to be from Celebes, and _O. Boisduvalii_, Montrouzier, from Woodlark Island. Var. _a_, Aru Islands (_Wall._). _O. Arruana_, Feld. Lep. Frag. p. 24. Individuals from this locality differ in the arrangement of the nervures; in some the third subcostal nervure of the upper wings branches from the same point with the upper disco-cellular, in others considerably beyond it; the points from which the subcostal nervures branch also vary. The amount of green colour on the median nervure and its branches varies. In some specimens there is a spot at the anal angle of lower wings beneath, agreeing with _O. Pronomus_, G. R. Gray; but this is generally wanting. Var. _b_, Dorey, Salwatty, south-west coast of New Guinea (_Wall._). These agree very closely with _O. Poseidon_, as figured by Westwood; they differ individually in the same manner as the last, and also in the length of the lower disco-cellular nervure on the under wings. They have generally no golden spots beneath the wings. They vary also in the outline of the under wings, the outer and anal angles being more acute in some specimens than in others. Some have the under wings of a uniform green entirely without spots, while others have a range of black spots more or less fully developed. Var. _c_, Waigiou (_Wall._). _Archideus_, G. R. Gray, ♀. This agrees with the last; but the male is of a more delicate green than any of the others, and has less of that colour on the median veins. On the under side there are no golden spots. The whole surface has a golden tinge, and the central portion of the lower wings is tinged with amber-brown. The females of all the above vary extremely, much more even than the males, and from the same locality two specimens are rarely alike. The discoidal cell is in some specimens more than half occupied by a whitish patch, while in others there are only a few small spots. One of my specimens from Salwatty almost exactly agrees with that figured by Westwood (Cat. of Or. Ent. pl. 14) as from Cape York. One of the Waigiou specimens is the same as _Archideus_, G. R. G., figured by Boisduval (Voy. de l’Astrolabe, t. 4. f. 1, 2); and another, from New Guinea, differs very little from _Euphorion_, G. R. G. (Brit. Mus. Cat. Lep. pt. 1. pl. 2. f. 3), from North Australia.