Moth Flies Moth flies are common, frequently-abundant insects also known as drain flies. The name moth fly refers to this insect's superficial resemblance to a tiny moth. A fuzzy appearance is caused by a dense covering of long hairs on the body and wings. Drain fly is perhaps a more useful name for this insect because it describes one of the common sources of the flies in the home. These same flies are sometimes prevalent in sewage treatment plants where they are called filter flies or sewage flies.
Moth flies are of little importance except as an annoyance and nuisance.
They do not bite or sting. Although they could possibly be vectors of disease pathogens because of their points of origin, there is no evidence of actual transmission. They can also reproduce in other constantly-moist areas of decaying organic matter such as under dripping pipes and refrigeration equipment. Control of moth flies requires locating and eliminating larval breeding sites. If the flies are breeding in that drain they will accumulate underneath the film within a day or two.