News Education Wildlife Journal Federal Aid Calendar Hunting Fishing Hunter Ed . For one thing, the larvae of black flies and mosquitoes are an important food source for fish, including trout, bass and many other species. The adults also are eaten by birds, bats, and other insects.
Black flies breed exclusively in running water.
Their worm-shaped larvae hatch and attach themselves to submerged objects. There they filter the water, consuming bacteria and other microorganisms as they clean the water. You have all this stuff suspended in the water column, and they filter it out. It's basically mostly vegetable, which they concentrate into a meat, which is then fed upon by fish and whatever else feeds on aquatic larvae. Among the predators of black fly larvae are fish, insects, amphibians and others.