Drain Fly

Damp environments such as bathroom drains, sewage treatment plants, and moist compost.

Larvae feed on the organic gelatinous film (biofilm) that accumulates in drains; adults feed on liquid carbohydrates and water.

They are weak fliers and are typically seen crawling on walls or near drains. They are most active at night and lay eggs in moist organic matter.

They do not bite and are generally harmless to humans, but can be a nuisance in large numbers and may mechanically transport bacteria from sewage to food surfaces.