Moth Fly / Drain Fly / Sewer Fly

Order: Diptera
Family: Psychodidae
Common Name: Moth Fly / Drain Fly / Sewer Fly


The adult is about 1.5mm long, delicate and fuzzy. The color pale yellowish to brownish gray to blackish, depending on the species. It has a pair of antennae. Wings broadly oval, pointed apically, veins and margins hairy and held roof-like over body at rest. It is a non-biting fly.

Biology and Behavior

Flies have complete metamorphosis: egg, larva, pupa and adult. Adult females lay their eggs (30-100eggs) on the surface of the gelatinous film. Both larvae and pupae live in this gelatinous film too. Larvae feed on the algae, bacteria, fungi, microscopic animals of this film. Eggs hatch in 32-48 hours, the larvae stage last 8-24 days, and the pupal stage lasts 20-40 hours. Developmental time (egg to adult) takes 7-28 days, depending on situation. Adults typically live for 2 weeks.

Damage and Disease Caused

Moth fly is known as a nuisance.

Control Strategies

Take care of sanitary levels such as regularly cleaning gully traps, drains, sewer leaks, dirty garbage cans, clogged roof gutters, moist compost and septic tanks. Drain or gully trap can often be clean out with cleaners using brush followed by hot water. It is required to remove the gelatinous film lining.