The immature aquatic larval stage of the adult black fly is somewhat of an anomolie. While adult black flies are terrestrial organisms well know for their reputation as mammalian blood feeders, their immature larvae are quite the opposite. Shortly after the adult flies lay eggs in running water of creeks and streams, the larvae attach themselves to objects in the substrate such as rocks and lots. Their tiny mouths have unusual fan like structures which can be expanded to allow the larvae to catch tiny pieces of organic material floating by in the surrounding water. Like terrestrial termites, they have bacteria in their gut that allows them to digest cellulose, the major building block of plants. They are also an important food source for numerous fish and aquatic organisms. Individual species of black flies have specific intolerances to stream temperatures, current velocities and dissolved oxygen levels making them excellent bioindicators of water quality.
Quick Visual Description: usually found attached to the substrate, cylindrical brown, gray or black body with lighter colored club shaped head containing prominent pair of mouth brushes for feeding.