Gnats

The common name of the gnat is applied to certain small flies, and that of fungus comes from their common occurrence on fungi which serve as a major food source for their larvae, dark winged describes the smoke colored wings commonly found within the Sciaridae.

Adults are about 1/32"-7/16" long.  They are slender to moderately robust, long-legged, somewhat mosquito like.  They are colored usually black, brown or yellowish, sometimes brightly colored.  Wings are usually smoke  colored or sometimes patterned with darker areas.  Antennae is usually 16 segmented.

Mature larvae usually slightly longer than respective adults.  Sciarid larva with shiny black head and 12 segmented essentially featureless white translucent body.  Mycertophilid larva usually cylindrical and slender, with well developed head, and 11-12 segments.

Adults are typically found on or near larval food materials.  Larvae feed primarily on fungi growing in the soil and moist decaying organic matter.

Inside, fungus gnat infestation are almost always associated with the soil of over watered potted plants and atriums.  Secondarily, consider signs of water leaks or  moisture problems, such as water stains, peeling plants and atriums, swelling of walls or wall coverings, to indicate where fungi may be growing which can support larval development.

Outside, mulched areas and the soil associated with them is usually the source, especially if new mulch is added annually without removing the old first and/ or if sprinkler systems are present.

Adults are usually found in moist areas where larval food is present.  During the day, adults of many species congregate in dark moist places.  Some species are most active at dusk and less active at dawn.  Adults of most of the gnat species are attracted to light.

(Insect Information excerpted from the NPCA Field Guide to Structural Pests)