The Drain Fly
Drain flies are commonly found in humid and tropical regions, but the 2600 species of these flies are scattered all across the world. They are harmless pests that can be a nuisance nonetheless by infesting plumbing and sewage systems. Due to their moth-like appearance, they are also known as moth flies. They are small true flies belonging to the order Diptera.
HOW TO IDENTIFY DRAIN FLIES
Drain flies are easy to identify because of their unique appearance. Unlike house flies, blowflies or fruit flies, these flies are furry and have widely set apart flattened wings.
- Can be 1.5mm to 5mm long
- Dense coat of small hairs all over the body
- Flattened wings that are not closely connected at the centre
- Ovoid wings
- Six Legs
- Rainbow-like sheen on wings at times
- Furry, segmented antennae
- Wings are covered with scales
- Their larvae resemble wiggling, white worms
Appearance, Behavior, Signs

Drain Fly. By gbohne from Berlin, Germany – tropical moth fly (Diptera: Psychodidae) – indet., CC BY-SA 2.0,
Drain flies look like miniature versions of moths and are attracted to damp areas. Washbasins, washrooms, kitchens, plumbing units, and drainages are all areas where they frequently breed and thrive. These furry brown flies mate and lay eggs in stagnant water. They infest areas in large numbers, and so can be a nuisance. The decomposing organic material is what allows the flies to lay eggs that can hatch and start a new generation of flies. They usually breed outdoors in the summer.
Drain flies themselves feed on organic matter – decomposed or otherwise. Moisture is what is ideal for the drain flies. However, larvae of drain flies can survive drastic temperature and oxygen level changes. They breed at a rapid pace – in just two weeks you can have a full-blown infestation. They are not known to be carriers of any diseases. The drain fly can fly fast and are often hard to swat with a hand. Drain flies will also settle on other things, such as food (and this can lead to contamination).
Signs of these flies include spotting them resting on walls, pipes or inside washbasins. Bathroom walls are a favorite resting area for these flies. They are frequently found near rotting logs, compost pits and stagnant water bodies as well.