Horse Fly Bites

The most common type of horse fly (Family Tabanidae) found throughout North America measures around three-quarters of an inch in length and is typically black in color with a green or greenish-colored head. Horse fly wings are clear. Blood sourced from hot-blooded mammals, such as dogs, horses, deer, and humans, serves as a main source of nutrition for female horse flies. In order to retrieve blood meals, females wait for prey in shaded areas and attach to host mammals using what scientists refer to as “scissoring” mandibles that are able to dig deep into the flesh of their host. Unlike the female gender of the species, male horse flies almost exclusively consume fruit juices and nectar from flowers for sustenance.


Horse flies commonly bite areas around the necks and legs of victims thathave large, healthy arteries. The insects often swarm to feed, with as many as 100 horse flies converging on a single animal to draw blood meals. Dawn and dusk are the most common times of day female horse flies feed. The bites of horse flies are generally painful and result in lesions and swelling, depending on the part of the body affected. Females often leave noticeable, swollen wounds, sometimes visibly bleeding, once finished with a blood meal or shooed away. Barns or other ill-lit structures providing shade serve as ideal hiding/harborage spots for horse flies.

Potential for Transfer of Disease

Due to the deep penetrations of horse fly wounds and the aspect of feeding associated with the bites, the transmission of disease remains possible if sustained contact occurs. Bites should receive immediate attention. The possibility of disease transmission mainly comes from the multiple feedings that take place across several species of mammals in a given day or within relatively short periods of time which leave trace particles of flesh and blood from other animals on horse fly mandibles, which are then potentially transferred to subsequent hosts upon biting.


If bitten by the pest insect, victims should take appropriate actions to limit the possible transmission of disease and chances of infection. Soap and water solutions serve as acceptable means of cleaning a horse fly bite in addition to using saliva, which contains a protein that can often act as a temporary disinfectant until the proper materials are accessible to clean and dress the bite mark. If an allergic reaction occurs, Benadryl or other anti-allergen ointments and medicines may reduce the amount of swelling, itching, or general discomfort associated with such a reaction. Victims should avoid scratching the abrasion and visit a licensed doctor if pain, swelling, or significant reactions occur. On average, horse fly bites may take a week or so to fully heal. Bandages or other medical sutures may serve as barriers to limit the potential for infection and the ability to scratch at the wound while it heals.