Hybomitra difficilis

Horse Fly


Family: Tabanidae

Subfamily: Tabaninae

Length: typically 15-16 mm


In the Mountain State, this annoying fly is most common in May, June, and July. It attacks cattle and harasses humans.

Drees and colleagues (1980) noted that "even though this is a common species as an adult, larvae have never been observed."

Unlike closely related Hybomitra species, females of H. difficilis have bare rather than hairy eyes. (Any hairs present are not readily seen in the field or in photographs). Males, on the other hand, have as one of their key traits, stiff hairs where the eyes meet.

John F. Burger (1995) gives the range of this fly as "Wisconsin to Massachusetts, south to Oklahoma and Florida." West Virginia counties with records of the species are indicated on the map below.

Another species in this genus illustrated on the Insects of West Virginia website is Hybomitra lasiophthalma.

Hybomitra difficilis range map, West Virginia

A note about our maps