General: Black Flies (Prosimulium spp.) are a diverse group of flying insects representing several hundred species. Black Fly adults are small black, gray, or yellowish flies, which, if it weren't for their great numbers and biting habit, might go unnoticed. The larvae, however, are aquatic and often are seen attached to rocks in the flowing water of desert streams.

In many species of Black Flies, the adults feed on the blood of birds, or in a pinch, humans, causing a welt and itching. The larvae, however, are harmless.

Taxonomy: Order Diptera (Flies); Family Simuliidae (Black Flies)