Drain Fly


Actual Size: 1.5 to 5 mm

Characteristics: Small; short, hairy bodies and wings, giving them a furry appearance.

Legs: 6

Wings: Yes

Antennae: Yes

Habitat: Live and breed near standing water in drains, septic tanks, compost, and more.


  • Often appear in sinks and bathtub drains.
  • Get their name from the fact that they often breed in drains.
  • Can easily crawl through normal fly screens.

Drain Flies in Bristol

Drain flies are one of the smallest types of flies. Sometimes referred to as moth flies, belong to the family Psychodidae and get their name because they often breed in drains. They are found throughout the United States and can become an annoyance in homes, sometimes appearing suddenly from sinks and bathtub drains. They can breed in tremendous numbers in sewage treatment plants and then be carried away by the wind to nearby buildings, where they can crawl through ordinary fly screens.

Drain Fly Habitat

Drain flies develop in muck or gelatinous material that accumulates in sewage disposal beds, septic tanks, moist compost, or dirty garbage containers. They may also emerge from drains of sinks or bathtubs, from tree holes, rain barrels, moist organic solids, or bird nests which have accumulations of fecal material. Drain flies gather, mate, and lay eggs in moisture or standing water. The slimy film that forms in sewers and drains is a favorite breeding spot. Inside structures, they are strongly attracted to light and will be found on glass windows, doors, lamps, and around indoor lighting.

Drain Fly Behaviors & Dangers

Besides being a nuisance, drain flies are not particularly dangerous. They do not bite people or animals or do damage to structures or plants. However, because these flies originate from filthy sources, they have the potential of being mechanical vectors of diseases. Populations of these insects can become a nuisance in homes, and their presence is almost always linked to a clogged drain. In homes here in Tennessee, they are most often seen in or around bathroom drains. Drain flies are weak fliers and when encountered, they are often found crawling on walls and other surfaces.

If you have a drain fly infestation in or outside your Tennessee home, contact your local exterminators for help.