The adult females are blood feeders and are often serious pests, just go fishing when they are out and you will know what l mean.
Livestock has died from being bitten by a large number of black flies. They also transmit diseases to wildlife in North America, and to humans in other parts of the world.
The larvae are aquatic and occur in fast-moving streams. The larvae attach themselves to rocks and other objects by means of a sucker at the posterior end of the body and filter food from the water as it flows past.
Adults occur in late spring and early summer, often near the stream from which they emerged.
Black Flies are small grayish or blackish flies with short legs, broad rounded wings, and a humpbacked shape.