In the United States, a small, venomous, two-winged fly of the genus Simulium of several species, exceedingly abundant and troublesome in the northern forests; -- called also buffalo gnat. The larvæ are aquatic. It sucks the blood of birds as well as humans and other mammals.
A small gnat like swarming, annoying, biting insect that comes out usually around Memorial day thru the 4th of July.
an aquatic macroinvertebrate of the order Diptera, a true fly. Dumbbell-shaped, soft larvae attach themselves to the substrate and prefer soft sediment; they are pollution tolerant.