The Deer Fly (Chrysops spp.), also known as the “yellow fly”, is a fly of the family Tabanidae that can be a pest to cattle, horses, and humans. It is often found in damp environments, such as wetlands or forests. It lays clusters of shiny black eggs on the leaves of small plants by water. The aquatic larvae feed on small insects and pupate in the mud at the edge of the water.
The Deer Fly is often considered a horse-fly. A distinguishing characteristic is its patterned gold or green eyes. It is smaller than a wasp and has dark bands across its wings. While female deer flies feed on blood, males instead collect pollen. When feeding, females use their knife-like mandibles and maxillae to make a cross-shaped incision and then lap up the blood. They are potential vectors of tularemia and loa loa filariasis.
The bite becomes painful immediately. The best way to treat a bite is with alcohol to prevent infection. Benadryl cream (now available as a generic) is the best treatment to stop the terrible itching and swelling that many people endure from these insects. Apply the cream immediately, liberally, and often. The symptoms will subside quickly, usually within a half hour.