Tabanidae

Insect family that comprises the horseflies and deerflies.

Classification Tabanidae is in order Diptera, class Insecta, phylum Arthropoda.

There are usually eight to nine larval stages, which may develop over several years, the larva entering a resting phase (diapause) during winter. Some tropical species have two or three generations per year. The larvae are found in water, mud, swamp, and marsh-land, rotting leaves, logs, and tree-holes. Most are predacious upon other insect larvae, or feed on decaying plant material. In all but a few of the more primitive, tropical genera the females are blood-feeding; the males always feed on nectar, honeydew, and plant sap.

The females of three genera: Chrysops, Haematopota, and Tabanus, commonly attack humans and livestock sucking blood, and causing severe annoyance by their painful bites. The presence of these flies in very large swarms around cattle can cause the loss of so much blood that there is a large drop in the milk yield and a deterioration in their condition. Tabanids rarely attempt to engorge from any one feed, but seem to prefer to take frequent sips, often from different animals. This habit of interrupted feeding enables them to transmit a large number of diseases mechanically, that is the disease organisms do not develop within the fly, but are carried by it (for example on the mouthparts).

The disease organisms of anaplasmosis, anthrax, tularemia, trypanosomiasis, swamp fever of horses, and vesicular stomatitis are known to be mechanically transmitted in this way by tabanids. Chrysops species are also the vectors of loa loa to humans and monkeys in West and Central Africa. This filarial worm undergoes part of its development within the fly, which is therefore called its vector, as opposed to being a mechanical carrier.