Adults live about two weeks, with old ones dying and new ones emerging. They feed on flower nectar and polluted water. During the day, adults rest in shaded areas or on walls near plumbing fixtures and on the sides of showers and tubs. Most activity occurs during the evening when these flies are seen hovering about drains and sinks. They may breed in large numbers at sewage filter plants and then may be carried by prevailing wind to nearby homes up to a mile away.
Adults are small enough to pass through ordinary window screening.
Control Measures Drain flies do not bite humans but may become a nuisance by their presence in large populations. Sometimes it takes persistent effort to eradicate an infestation in the home. Concentrate on eliminating larval breeding sites from drains in floors, sinks, wash basins, bathtubs, etc. Sometimes the source of the problem is a nearby filter plant. To detect if flies are indeed coming from a drain, one needs to cover the opening during a down time with a series of glue boards.