Drain fly (moth fly)

Adults occur indoors near sinks, drains, bathrooms, and other damp organic sites; larvae develop in the gelatinous film inside drains or sewage systems.

Adults consume little or nothing, sometimes taking moisture or organic liquids. Larvae feed on bacteria, fungi, algae, and decaying organic matter in drain buildup.

Weak, erratic fliers often resting on walls near moisture; adults are commonly seen at night. Development from egg to adult can take roughly 1–3 weeks under warm conditions.

They do not bite or sting and pose little direct health risk, though heavy indoor infestations indicate dirty or blocked drains. Larvae help decompose organic material, but control usually requires scrubbing drain interiors and removing biofilm.