Utah State University Extension
Fungus gnats are small, long-legged flies in the families Mycetophilidae and Sciaridae. The dark-winged fungus gnat, Bradysia spp. is one of the most common indoor pests. Adults fly over plants, but consume only liquids and are harmless to plants.
Hodgson, Erin W. and Lambert, Brooke A., "Fungus Gnats" (2008). All Current Publications. Paper 905.