Drain fly (moth fly)

Moist, organic-rich sites such as sink, shower, and floor drains; larvae develop in drain slime and sewage-associated films.

Larvae consume microorganisms, algae, fungi, and decaying organic matter in drain biofilm. Adults feed little, mainly using stored energy and occasionally taking liquids.

Weak, fluttering fliers that rest on walls and surfaces; often active near plumbing at night. Several generations can develop annually in persistently wet drains.

They do not bite or sting and are not significant disease vectors, though large infestations indicate poor drain sanitation. Larvae contribute modestly to decomposition; cleaning and drying drains controls them.