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.


  • May appear suddenly from sinks and bathtub drains.
  • Get their name from the fact that they often breed in drains.
  • Being tiny flies, they can easily crawl through normal fly screens.

Drain Flies in Jacksonville FL

Drain flies, also called 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 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 that 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 indoor lighting.

Drain Fly Behaviors, Threats, or Dangers

Drain flies 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 residential homes, the most common breeding sites are bathroom drains. Drain flies are weak fliers and when encountered, they are often found crawling on walls and other surfaces.

If you are dealing with a drain fly problem in your property, contact your local fly exterminators.