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Life in Freshwater

Midges - Black Fly (Simulium spp)

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Black Fly larva

The fly is between 2 - 6 mm long depending on the species. They are all black and the females bite humans. The larva is aquatic and is found attached to vegetation and stones, up to 8mm in length.

The group is prolific whereever there is a plentiful supply of fast flowing water. This makes them particularly unpopular in highland regions of Europe, e.g. Scotland, where rivers and streams can breed swarms.

ECOLOGY: These biting midges are associated with rivers and in Africa they are the vectors of the disease River Blindness. Luckily the European flies are just a nuisance and it is thought that they do not carry disease. After consuming a drop of human blood the female lays her eggs in the water. The larva develops a series of strategies for its survival. The fast current can easily dislodge it even though it has a kind of sucker at the end of the abdomen. It is in fact a disc with small hooks. It moves by looping itself along holding the surface with the disc and a single proleg near the head. If swept away it throws out a life line - a silk thread which gets caught in stones or vegetation. It then hauls itself in. The brush-like mouthparts pick up bacteria, detritus and diatoms swept along in the current. When the larvae pupate they form groups of folded cocoons to protect the pupa (see image below).

Black Fly pupae on rocks in fast flowing river

See also Midges (Chironomids and Phantom) and Mosquitoes Also Horseflies










Diptera - true flies

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