Adults are 1/16 to 3/16 inch long. Fungus gnats are dark-colored, tiny, delicate flies that are attracted to light from computer screens, televisions, lights, and windows. Mature larvae are about the same length as adults with a dark head and whitish body with few features.

Fungus gnats are associated with overwatered houseplants but can appear in other places. The larvae of fungus gnats feed on fungi and moist decaying matter found in rich soils and moist areas associated with leaks, peeling paint, or rotting wood.

Fungus gnats do not cause damage to structures or human health, but they are a good indicator of a moisture issue that needs to be addressed.