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Horse Fly

Horse Fly, Scientific Name 

Horse-flies are true flies in the family Tabanidae in the insect order Diptera. They are often large and agile in flight, and the females bite animals, including humans, to obtain blood. They prefer to fly in sunlight, avoiding dark and shady areas, and are inactive at night. They are found all over the world except for some islands and the polar regions.

Adult horse-flies feed on nectar and plant exudates; the males have weak mouthparts and only the females bite animals to obtain enough protein from blood to produce eggs. The mouthparts of females are formed into a stout stabbing organ with two pairs of sharp cutting blades, and a spongelike part used to lap up the blood that flows from the wound. The larvae are predaceous and grow in semiaquatic habitats.

Female horse-flies can transfer blood-borne diseases from one animal to another through their feeding habit. In areas where diseases occur, they have been known to carry equine infectious anaemia virus, some trypanosomes, the filarial worm Loa loa, anthrax among cattle and sheep, and tularemia. As well as making life outdoors uncomfortable for humans, they can reduce growth rates in cattle and lower the milk output of cows if suitable shelters are not provided.

Horse-flies have appeared in literature since Aeschylus in Ancient Greece mentioned them driving people to madness through their persistent pursuit.

Diseases Vectored by Horse Flies

Johann Wilhelm Meigen's Europäischen Zweiflügeligen 1790, Plate CXCIV. Nos 7, 8 and 9 are Haematopota horse-flies, H. crassicornis, H. grandis and H. pluvialis respectively.
Tabanids are known vectors for some blood-borne bacterial, viral, protozoan and worm diseases of mammals, such as the equine infectious anaemia virus and various species of Trypanosoma which cause diseases in animals and humans.[40] Species of the genus Chrysops transmit the parasitic filarial worm Loa loa between humans,[41] and tabanids are known to transmit anthrax among cattle and sheep, and tularemia between rabbits and humans.[40]

Blood loss is a common problem in some animals when large flies are abundant. Some animals have been known to lose up to 300 millilitres (11 imp fl oz; 10 US fl oz) of blood in a single day to tabanid flies, a loss which can weaken or even kill them. There are anecdotal reports of horse-fly bites leading to fatal anaphylaxis in humans, an extremely rare occurrence.[42][43]

Horse Fly Management

Controlling horse-flies is difficult. Malaise traps are most often used to capture them and these can be modified with the use of baits and attractants that include carbon dioxide or octenol.[44] A dark shiny ball suspended below them that moves in the breeze can also attract them and forms a key part of a modified "Manitoba trap" that is used most often for trapping and sampling Tabanidae.[45] Cattle can be treated with pour-on pyrethroids which may repel the flies, and fitting them with insecticide impregnated eartags or collars has had some success in killing the insects.

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