Drain Flies

Also called moth flies, sewer flies or filter flies these true flies have bodies and wings covered with numerous hairs. If crushed they leave a powdery smudge

Drain flies, or moth flies, can be found in moist, highly organic debris areas such as sink drains, sewage treatment facilities, storm drains, dung and rotten vegetation.

Adults range in size from 1/16 to ¼ inch . They may be yellow to brown /black in color.

During daylight, they will often be found resting on walls near drains.

Adult female drain /moth flies most often lay their eggs in masses on the surface of gelatinous film found in drains and sewers.

They may also breed in moist, shady areas outdoors such as under potted plants, in bird feeders and baths, in moss, in clogged roof gutters, under air conditioners, in thick mulch, or on wet ground areas.

The larvae feed on decaying material that collects in drains. In natural settings, moth fly larvae feed on decaying plants and animals. Most moth flies are harmless to humans, though they may transmit bacteria and other microorganisms from their breeding sites to areas where people are. Moth flies do not bite. Adults live about two weeks

Control

Finding the sources of breeding and eliminating them is the best control.

Floor drains, overflow cuts in sinks and tubs, sump pump pits and sewers can accumulate organic matter but often do not receive enough water to flush the waste down the drain.

They may be common in laundry and floor drains, toilet and shower drains.

  

The drain/moth fly larvae feed on the sides of the drain and in the drain trap if there is an accumulation of organic debris there. You can check it by placing some tape over the opening (leave some opening for air flow). If you find these flies stuck to the tape , you have discovered the source.

Pouring bleach down the drain is not effective. A bacterial digester  may be used to break up the organic debris.

 Re-grouting tiles to prevent water seepage into walls will stop breeding in those sites. If found in rotting vegetable matter, the source should be destroyed.

Clean dirty garbage containers, wet lint under the washing machine, and even standing water in containers under houseplant pots. Outside the home, inspect air conditioners, bird baths, shallow stagnant pools of water and sewage treatment facilities upwind as adult flies will travel with the wind.

If adults do not disappear within a week further treatments or looking for other breeding sources is needed .