Horse-fly

''For the American band, see The Horse Flies

Horse-flies (family Tabanidae) are among the world's largest flies. These flies are often considered pests because of the painful bites that many, though not all, of the species can inflict on animals and humans. They occur worldwide, being absent only at extreme northern and southern latitudes. Flies of this type are among those known sometimes as "gadflies" or "clegs".

A type of insect, horse-flies are classified in the fly order Diptera. There are approximately 3,000 species of horse-flies known worldwide, 350 of which are found in North America. At least three subfamilies are recognised:

Chrysopsinae
Pangoniinae
Tabaninae
the genus Zophina is of uncertain placement, though it has been classified among the Pangoniinae.

The two best-known types are the common horse-flies, genus Tabanus Linnaeus, 1758 and the deer-flies, genus Chrysops Meigen, 1802 also known as banded horse-flies because of their coloring. Both these genera give their names to subfamilies. The "Blue Tail Fly" in the eponymous song was probably a tabanid common to the southeastern United States.

Contents

1 Diet
2 Sight
3 Bite
4 Habitat
5 Predators
6 Reproduction
7 Diseases

7.1 Citation

8 See also
9 Gallery
10 External links

Diet

Adult horse-flies feed on nectar and other plant juices; the females also feed on blood. Males lack the necessary mouth apparatus to do so. Most horse-flies feed on mammal blood, but some species are known to feed on birds, amphibians or reptiles.

Sight

The females' primary sense for locating prey is sight, and they have large compound eyes that serve this purpose well. The flies usually lay waiting in shady areas for prey to happen by. They are attracted to large, dark objects, and to certain animal odors and carbon dioxide. They are also attracted by motion, their eyes being well adapted to its detection. The eyes of horse-flies are generally brightly colored, and this coloration is one of the means entomologists use to identify them to species, though the colors rarely persist after death. Sex can be distinguished based on size of the eyes relative to the frons.

Bite

A horse-fly's bite can be very painful. Unlike insects that pierce the skin, horse-flies have mouth parts that work like miniature knives, which they use to slash open the skin with a scissors-like motion. This causes the blood to seep out as the horsefly licks it up. When attacking humans, the flies generally prefer the head and upper body regions, going unnoticed until a bite is inflicted.

Habitat

Horse-flies are most active in hot weather, mostly in summer and autumn during the daylight hours. Most species also prefer a wet climate, which makes it easier for them to breed.

Predators

Aside from generalized predators such as birds, there are also specialist predators such as the Horse Guard, a type of Sand wasp that preferentially attacks horse flies.

Reproduction

Eggs are generally laid on stones close to water or on plant stems or leaves. On hatching, the larvae fall into water or moist earth, feeding voraciously on invertebrates, such as snails and earthworms, and small vertebrates.

Diseases

Some horse-fly species are known to transmit disease and/or parasites. Species in the genus Chrysops are biological vectors of Loa loa, transmitting this filarial worm between humans.

A common problem in some animals, though, when large flies are abundant, is blood loss. Some animals have been known to lose up to 300 ml of blood in a single day, which can severely weaken or even kill them.

Citation

"Although the tsetse flies were responsible for transmitting sleeping sickness in most areas, occasionally an epidemic occurred in which the disease might be conveyed to cattle by direct contact with the ordinary horsefly, tanidae. This probably occurred when swarms of these flies surrounded the wretched animals. In one such epidemic some 3000 head of cattle died of trypanosomal disease in northern Rhodesia. Sir David and Lady Bruce returned to England in 1913. David Bruce reported the results achieved by this Sleeping Sickness Commission of the Royal Society in the Croonian Lectures in 1915." [link]

Gallery

Image:Tabanid_wynaad.jpg|A Tabanid from the Western Ghats

External links

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