Black Fly

The Black Fly is also known as the Family Simuliidae, which contains 166 species in North America. They are between 1/16-1/8" (2-4 mm) in length, have a humpbacked, downward pointing head, thick antennae with many segments, smoky heavy veinged wings, and are grayish brown to shiny black in color.

  • Both the male and female feed on nectar. The female sucks blood from birds and mammals. Larvae are filter feeders, eating particles such as diatoms and bacteria.
  • Eggs are laid on stones or leaves at the edge of rapidly flowing streams, or on the water surface itself. Larvae tumble into water. Fully grown larvae pupate in cocoons that coat rocks in water, resembling moss. Adults burst out, rise on a bubble of trapped air, and fly away in late spring and early summer.
  • Black flys can be found near running water in forests, mountains, and tundra, from Labrador south to Georgia, west to California and Mexico, north to Alaska.
  • Biting adults are the bane of the North Country and mountain resorts, particularly early in the season. Some species transmit waterfowl malaria, which accounts for up to half of the deaths of ducks, geese, swans, and turkeys.
  • Warning: Female sucks blood from birds and mammals. Not known to transmit diseases to humans in North America.