Note 68 — Family HIRUNDINIDÆ.—The Swallows.

Progne, (subis var?) leucogaster. Progne leucogaster, Baird, Rev. Am. B. 1865, 280. (Southern Mexico to Carthagena.) Progne dominicensis and P. chalybea, Auch. (nec Gmel.).

From a careful examination of specimens of the above forms, the opinion that they are all local differentiations of one primitive type at once presents itself. The differences from the typical subis are not great, except in the white-bellied group (dominicensis and its allies), while an approach to the white belly of these is plainly to be seen in P. cryptoleuca; again, some specimens of dominicensis have the crissum mixed with blackish, while others have it wholly snowy-white. While the male of cryptoleuca is scarcely distinguishable, at first sight, from that of subis, the female is entirely different, but, on the other hand, scarcely to be distinguished from that of dominicensis and leucogaster. Adult males of the latter species are much like adult females of dominicensis, while Floridan (resident) specimens of subis approach very decidedly to the rather unique characters of elegans. It is therefore extremely probable that all are merely local modifications of one species.