T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Fly (Horse fly) Family: Tabanidae

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Suborder: Brachycera
Infraorder: Tabanomorpha
Superfamily: Tabanoidea
Family: Tabanidae
Common names: Horse Fly, Deerfly, Gladfly, March fly.

Worldwide about 4,500 species of Tabanidae have been described. They are commonly called horse flies or deer flies. A horse fly is a true fly whose females habitually attack humans and livestock and are widely regarded as pests because of the bites that females that most species inflict, and the diseases and parasites that some species can transmit. Adults can be up to 25 mm long. They are black to dark brown in colour with green or black eyes. The males have contiguous eyes, which easily differentiates them from females whose eyes are widely separated.

They are most active during daylight hours. The males flies are mainly pollen and nectar feeders. Most female horse flies feed on mammalian blood (like mosquitoes) but some species are known to feed on birds or reptiles. The females have a small sharp knife attached to their mouth that they use to slash open the skin. The protein in the blood is necessary for the eggs to ripe. A bite can be very painful.

The adult life cycle is 30 to 60 days. The female lays up to >1000 eggs on a vertical surface overhanging water or wet ground which is favourable to larvae development. The eggs hatch in 5–7 days. They overwinter in the larval stage and pupate during the spring and early summer. The larva is predators of small invertebrates in moist environments, such as in mud on the edges of bodies of water, in damp soil, under stones, or in rotting logs.

Female fly. These species eyes are separated.

The underside 

Another species.

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0