common name: Horse Fly
scientific name: Order Diptera, family Tabanidae, Tabanus spp.
size: Adult--1/4" to 1"
identification: Larger than house flies, usually darker with larger eyes. Some horse flies are jet black. Hair is all short and fine, not bristly. Eyes are often brilliantly colored.
biology and life cycle: Eggs are laid on vegetation in marshy areas. Larvae are predaceous on small insect larvae, worms, and crustaceans.
habitat: Flowers, excrement, and decaying organic matter.
feeding habits: Females are animal-blood feeders. Bites are painful. Males eat nectar from flowers.
economic importance: Horse flies are vectors of several diseases and can be troublesome to livestock and humans.
natural control: Fly parasites, flycatchers and other birds.
organic control: Fly swatters and natural diatomaceous earth fed to animals. Releasing the beneficial insect called the fly parasite, or dump fly, will eliminate any infestation. Citrus oil sprays will also kill them.
insight: These stout, broad-headed flies that are usually dark-colored and often have brightly colored eyes. Their flight is usually silent, unlike that of house flies, and they deliver a painful bite in search of a blood meal. Only the females bite; the males feed on nectar and pollen.
Compost offers powerful biological fly control. Composting organisms like bacteria, fungi, mites, insects, and even small animals add in the decomposition of animal dung and attack immature flies in the manure.
A Malcolm Story
These flies were a big nuisance on the farm. After working in the fields on hot summer days, we would go swimming in the stock tanks. The horse flies would always wait until we were in the water before they would attack. For some reason, they would rather bite a wet body than a dry one, and they were always smart enough to land on our backs so we couldn't swat them. Our only defense was to quickly dive under the water before the fly could bite. If one did manage to bite, and usually they did, it was a pretty sharp sting; but the sensation lasted only a moment and there was no swelling or other aftereffects.