Chrysops niger and Chrysops calvus
According to Peuchman and Teskey in the Manual of Nearctic Diptera, flies in the genus Chrysops usually have "at least a dark crossband" on the wing, or if the wing is unpatterned, then "gena without pollen." On the antenna, the scape and pedicel are about the same length (McAlpine, 1981).
Chrysops niger and C. calvus are two very similar species, both widespread in West Virginia. Records of C. calvus in the Mountain State have come from a narrow window between 20 May and 25 June. Records of C. niger have come from 12 May through 5 July.
A diagram at the bottom of this page shows one difference in the head of the two species, best seen in a true dorsal view. Drees and co-authors (1980) also comment that in Chrysops calvus the "sublateral thoracic stripes are very distinct," while in C. niger they are indistinct.
Differences in the dark coloration in the ocellar area in
Chrysops calvus and Chrysops niger.
Artwork based on an illustration in Drees et al. (1980).