The nematoceran family Psychodidae (moth flies or drain flies) are small (<2 mm) true flies (Diptera) with short, hairy bodies and wings giving them a “furry” moth-like appearance. The adults have long antennae and the wings are leaf-shaped, either slender or broad, with the most elementary wing venation of any Diptera, having little more than a series of parallel veins without crossveins. Adult Psychodidae are typically nocturnal though they orient themselves around lights and may appear to be attracted to light.
As a nuisance, they are associated with damp habitats in human bathrooms and kitchens. The larvae of the subfamilies Psychodinae, Sycoracinae and Horaiellinae live in aquatic to semi-terrestrial or sludge-based habitats, including bathroom sinks, where they feed on bacteria and can become problematic. Prevention is best accomplished by removing food sources such as hair clogs in drains.
The adults live for about 20 days, during which they will breed only once. Adults lay their eggs just above the water line inside moist drains. Sometime later, these eggs hatch into drain worms. The dark 6–7 mm long larvae are similar to those of mosquitoes in that they breathe through a small tube located at the back end of their narrow, maggot-like bodies. These larvae can sometimes be seen crawling along the moist edges of crevices in shower stalls or bathtubs. The insects complete their pupation stage submerged/ wet, and the adults then hatch at or under the waterline