Name: Tabanus spp.

Alias: Horse Fly. These large flying insects are hard to miss. They look similar to house flies, but they are about three or four times bigger. They come in various shades of grey and brown. Their eyes are broad, giving them the appearance of an Air Force fighter helmet. Females have a line between their eyes, but male eyes are almost touching. Adults generally feed on plant material, although the females supplement their diet with blood. Eggs are generally laid on solid surfaces near water. The larvae generally grow in semiaquatic habitats.

Crimes: The females have large cutting mouthparts that look like tin snips, which they use to cut open skin and suck blood out of mammals. Horses are a favorite target, hence the name. But they are not limited to horses only. Males have weak mouthparts and are generally just annoying.

Redeeming Qualities: The larvae are known to feed on the larvae of other pests such as other flies and mosquitoes.

Sentence: Control is usually considered for livestock only. Generic bug repellent is usually considered enough for humans. For livestock, the best options are permethrin-based fly killing sprays. They are available at any farm and ranch store. If your horse doesn’t care for being sprayed there are also dust forms to apply. Many of these dust forms are restricted use, due to inhalation hazards to humans. Be sure to always follow and read the label instructions.

For more information on dangerous and beneficial bugs, call UI Extension educator Joseph Sagers at 208-270-4031 or email