Black fly

A black fly (sometimes called a buffalo gnat, turkey gnat or white socks) is any member of the family Simuliidae of the Culicomorpha infraorder. They are related to the Ceratopogonidae, Chironomidae, and Thaumaleidae. There are over 1,800 known species of black flies (of which 11 are extinct). The majority of species belong to the immense genus Simulium. Like mosquitoes, to which they are related, most black flies gain nourishment by sucking the blood of other animals, although the males feed mainly on nectar. They are usually small, black or gray, with short legs and antennae. They are a common nuisance for humans, and many U.S. states have programs to suppress the black fly population. They spread several diseases, including river blindness in Africa (Simulium damnosum and S. neavei) and the Americas (Simulium callidum and S. metallicum in Central America, also S. ochraceum in Central and South America).

Regional effects of black fly populations

 * In the wetter parts of the northern latitudes of North America, including parts of Canada, New England and the Upper Peninsula of Michigan, black fly populations swell from Mid-May to July, becoming a nuisance to humans engaging in common outdoor activitites such as boating, camping and backpacking.
 * In Canada, black flies are a scourge to livestock, causing weight loss in cattle and in some cases, death.
 * The Commonwealth of Pennsylvania, in the United States, operates the largest single black fly control program in North America. The program is seen as beneficial to both the quality of life for residents and to the state's tourism industry.

Ecology
Eggs are laid in running water, and the larvae attach themselves to rocks. They use tiny hooks at the end of their abdomen to hold on to the substrate, often using silk holdfasts and lines to move or hold their place. They have foldable fans surrounding their mouths. When feeding, the fans expand, catching passing debris (small organic particles, algae and bacteria). Every few seconds, the larva scrapes the fan's catch into its mouth. Black flies depend on lotic habitats to bring food to them. They will pupate under water and then emerge in a bubble of air as flying adults. During this emergence, they are often preyed upon by trout.

Black flies are univoltine, which means that they spend the winter in the larval stage, often under the ice, where they slowly mature.

The Canadian Shield is characterized by an abundance of lakes and swift-flowing streams and hence offers optimum conditions for black flies to lay their eggs. The Canadian Shield is notorious for the abundance of black flies in the summertime.