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.
From these facts I am led to conclude that we have here a variable form spread over an extensive area, and kept variable by the continual intercrossing of individuals, which would otherwise segregate into distinct and sharply defined races. The same area is inhabited by many species of birds common to all parts of it; and just as the birds of Ceram and Amboyna are almost all distinct species from those of New Guinea, so do we find those islands inhabited by the Ornithoptera Priamus, a well-marked and constant species, readily distinguishable in either sex from the inconstant forms of New Guinea proper. The same parallel holds in North Australia. Many New Guinea species of birds extend, with very slight variation, to the country about Cape York; but when we reach the Moreton Bay district all these have disappeared, and we find only true Australian species. So the variable forms of O. Poseidon reach North Australia and Cape York, while in the Moreton Bay district we find the comparatively well-marked species O. Richmondia. Similar causes, whether geographical or climatal, have thus produced an analogous distribution in these widely separated groups of animals.
3. Ornithoptera Crœsus, Felder.
O. Crœsus, Feld. Wien. Ent. Monats., Dec. 1859. O. Crœsus, G. R. Gray, Proc. Zool. Soc. 1859, p. 424.
Hab. Batchian (Moluccas) (Wall.).