The relationships among the species of these large fruit-eating bats, commonly termed "flying foxes," are obscure and the genus is in need of revision. The basic, definitive work is still that of Andersen (1912). Tate (1942) and Felten (1964a, 1964b) have offered some additional remarks but groupings and suggested relationships of species of Pteropus almost entirely are the products of Kund Andersen. According to present-day concepts of variation and speciation, Andersen's criteria are artificial.
Basically, there are three "species-groups" of Pteropus in the Solomon Islands. The first is composed of species in which the rostrum is "unshortened" (its length about one third of greatest length of skull), and the cheek-teeth are of moderate size (M1 is 2.8-3.2 wide). The species are P. hypomelanus, P. admiralitatum, P. tonganus, and P. howensis. The first and second species were placed in the Pteropus hypomelanus group by Andersen (1912:98).
In the second group the rostrum is "shortened" (its length less than one third of greatest length of skull) and the cheek-teeth are of moderate to large size (M1 3.3-4.1 wide). Pteropus rayneri, endemic to the Solomons and represented there by at least seven subspecies, fits into this category.
The third group is represented by P. mahaganus and P. woodfordi. Both species are endemic to the Solomon Islands. In these species the rostrum is unshortened but the cheek-teeth are greatly reduced, especially in width (M1 is 1.0-2.2 wide). Both P. mahaganus and P. woodfordi can be included in the Pteropus scapulatus group of Andersen (1912:402).
Pteropus hypomelanus
Pteropus hypomelanus is a wide-ranging species of flying fox having at least seven subspecies; three occur in southeastern Asia, two on and near Celebes, and two in New Guinea and islands adjacent to the southeastern coast of New Guinea, including one island in the Solomons (Ellerman and Morrison-Scott, 1966:95; Laurie and Hill, 1954:32-33).
Fig. 5. Distribution of Pteropus hypomelanus luteus (