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Drain fly, Moth fly

Most recently reviewed by: Janet Hurley & Pat Porter (2018)

Common Name(s): Drain Fly, Moth Fly

Pest Location

Urban Structural


Adults are small and very hairy, with a pair of pointed wings. They resemble small moths because they hold their wings roof-like over the body when at rest. They are weak fliers and appear to hop or jump.

Origin and Distribution

A nuisance when numerous in and around homes and structures in the close vicinity of breeding habitats; larvae considered beneficial, an essential part of the cycle that breaks down waste into water soluble compounds; medically harmless.

Habitat & Hosts

Larvae have chewing mouthparts. Drain flies are common around sink drains, sewage treatment facilities, storm drains, dung and rotten vegetation. Larvae are aquatic or semi-aquatic, feeding on bacteria, fungi, algae and other microorganisms present in decaying organic matter. They often feed in the liquid or slime layers which develop around debris in drains, sewage treatment beds and standing water. However, when food is scarce they may become cannibalistic. Larvae are capable of surviving temperature extremes and habitats low in oxygen.

Life Cycle

Eggs, laid by females hatch into pale-colored larvae. Following a feeding period, larvae pupate and soon emerge as adult flies. Adults live only 3 to 4 days without food, but they can survive for weeks if nectar or other liquid carbohydrate food sources are available.


If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

These flies are found in areas of high moisture — in and around drains, septic systems, grease traps and other areas containing very moist organic solids. Adults are attracted to the gelatinous mass that develops in these areas to lay eggs. Larvae feed on algae, bacteria, fungi and the sludge in this film. Infestations could indicate a cracked or damaged sewer pipe or a dry drain trap.

Cultural, physical and mechanical management options are the best strategies and include posting notices to encourage the cleanup of spills, proper food storage and trash/recycle handling, elimination of standing water, fixing plumbing leaks, drying mops, emptying mop buckets and inspecting incoming produce and rejecting any infested or overripe product.

Not generally considered a pest, see related publications for more information.

Related Publications

IPM Action Plan for Small Flies peer reviewed management plan for the most common structural small flies.

Drain flies (moth flies or filter flies) Texas A&M AgriLife Extension Entomology publication

Bugwood Images