Drain fly (larva)

Natural Habitat

Moist environments containing organic matter, such as drains, sewage treatment plants, septic tanks, and compost piles.

Diet & Feeding

Decomposing organic matter, algae, bacteria, and fungi (as larvae).

Behavior Patterns

Larvae live in the gelatinous film that forms inside drains. They are generally nocturnal as adults and poor fliers, often seen resting on walls near drains.

Risks & Benefits

Generally harmless to humans but can be a nuisance in large numbers. In some cases, they can mechanically carry bacteria from sewage to food surfaces, though they do not bite or transmit blood-borne diseases.

Identified on: 2/19/2026