Drain Fly

Drain Fly
  • Size: About 2 to 5 mm long
  • Color: Gray to black
  • Distinctive Feature: Body covered with hairs, resembles small moths
  • Habitat: Drains, sewers, damp and poorly ventilated environments


The drain fly, also known as Psychoda, has distinctive features that facilitate its identification. As an adult, it measures about 2 to 5 mm in length. Its color varies from gray to black, with a slightly hairy body, giving a blurry or fluffy appearance. Its wings are wide relative to its body and have a unique shape, often described as leaf-like or heart-shaped when folded. The eyes of the drain fly are prominent, and it has long, thin antennae with many segments, contributing to its distinct look.


Drain flies thrive in damp and poorly ventilated environments. They are often found in bathrooms, kitchens, basements, and any place where moisture is present. These insects breed in decaying organic matter, particularly in residues that accumulate in drains, hence their name. Unclean pipes, sinks, showers, and even compost bins can become favored breeding sites for these flies.


Drain flies are primarily active at night. They are attracted to light, which makes them more visible when they fly around lamps or screens. Their flight is generally slow and erratic. These flies are not known to be disease vectors, but their presence in large numbers can be annoying and indicate an underlying hygiene or plumbing problem. They feed on decaying organic matter and can live from a few days to several weeks, depending on environmental conditions.

Distinguishing Drain Flies from Other Insects

Indian Meal Moth

Indian Meal Moth

The Indian meal moth, a moth species, is easily distinguishable from the drain fly by its thread-like antennae and its wings when at rest, forming a sort of roof over its body. Colored brownish with distinct patterns on the wings, the Indian meal moth measures about 8-10 mm, being larger than the drain fly. It is known for infesting dry products such as cereals, a different habitat from drain flies.

Fruit Fly

Fruit Fly

The fruit fly, often called the “fruit fly,” is easily recognizable by its distinctive red eyes and slimmer body. Measuring about 3 mm, it is smaller than the drain fly. Its coloration is generally yellow to brownish. It is attracted to decomposing fruits and fermented materials, a different habitat and food source from drain flies. The fruit fly has transparent wings and a less hairy body shape.

Phorid Fly

Phorid Fly

Unlike the drain fly, the phorid fly is known for its erratic flight and ability to run quickly on surfaces. It is generally smaller, measuring between 0.5 and 6 mm, and has a humped thorax, giving it a distinctive profile. The phorid fly has shorter wings relative to its body and does not have the characteristic hairy aspect of the drain fly. It is also known for its unique breeding behavior, often developing in a wide variety of decaying matter, including animal carcasses.

House Fly

House Fly

The house fly is significantly larger than the drain fly, measuring about 6-7 mm in length. It has a gray body with four longitudinal black stripes on the thorax. Its eyes are relatively larger, and its wings, when at rest, overlap. Unlike the drain fly, the house fly is often found in areas where food waste and feces are present, preferring a more varied and less specialized diet.

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