Moth fly (Diptera: Psychodidae)
Moth flies (order: Diptera) are in the family Psychodidae. Entomologists often refer to insects using a shortened version of the family name. In this instance, I refer to the referenced flies as “Psychodids.”
Psychodids are small (1/16”-3/16”) long, delicate, fuzzy, brown-gray flies that resemble tiny stealth bombers. According to BugGuide, about 113 species are found in our area, with more than 3,000 described species found worldwide.
Indoors, Psychodids can be seen resting on walls or other vertical surfaces near drain openings in rooms such as bathrooms, kitchens, and laundry rooms. Adult females lay eggs on the surface of the wet, gelatinous film that coats the insides of drain pipes. Larvae and pupae live in and feed on organic matter such as algae, bacteria, fungi, microscopic animals, and sludge in the film.
Although these flies breed in sewage, they do not bite and do not appear to transmit human pathogens (diseases).
Management of Psychodids is relatively simple: use a stiff drain brush to manually remove the organic matter from the sides of the drain pipes where eggs are laid and larvae feed.