The females of these two species are markedly different in colour, yet the males resemble each other so closely that Bradley (1913) was unable to distinguish between them. Waterston (is Chrystal, 1928) separated the males by the proportions of the hind metatarsus ; that of U. albicornis F. was “barely five times as long as broad,” while in U. flavicornis F. the metatarsus was “nearly seven times as long as broad.” However, Waterston had but two males of one species, and the metatarsal proportions vary intraspecifically ; on this account, the value of the character cannot be determined without a long series.