Drain Flies
Some Quick Facts About Drain Flies
Drain flies can appear without warning, and they are a nuisance in homes as well as in sewage disposal facilities. The adults of the species can become so abundant that they cover windows in the daytime and lampshades at night. They may pile up around sinks, tubs, showers and drains. They will get into outdoor drains as well. These flies grow in filth, so there is a chance of them transmitting human diseases.
Adult drain flies are very small – from one-fifth to one-sixth inch long. They appear fuzzy, and their coloring is dark gray. The wings and body are covered with dense hairs. They have long antennae, and their wings look too large for their body. They fold their wings on top of their body when not in flight, and resemble a moth when at rest. Drain flies are not strong fliers, and fly a few feet at a time in jerky movements. Their eggs are very small, and are cream or brown-colored. Their larvae have no legs, and are about three-eighths of an inch long. They appear gray and worm like, and the ends are darker than the mid-section.
Drain flies usually breed in shallow or polluted water. The eggs, larvae and pupae are found in the slime and muck around the sides of drains or in sewer beds. Eggs are laid in the same muck, and they usually hatch in thirty-two to forty-eight hours. Larvae eat the decaying matter, and other filth in the drain. In nine to fifteen days, the larvae have matured. They actually help to clean sewage water during this phase.
Pupae occur on the surface of the area they were bred in, and after twenty to forty hours, new adults emerge. It may take one to three weeks for the life cycle to be completed. Adults only live for around two weeks. They eat flower nectar and polluted water. Adults rest in shady places during the heat of the day. They are more active in the evening, when they hover around sinks and drains. Even adult drain flies can pass through ordinary window screens, so you're not immune just because you're inside.
Drain flies don't bite people, but they can become troublesome in large swarms. If you have an infestation in your house, eliminate the breeding sites for the larva first – drains from bathtubs, sinks, floors, etc. If they didn't originate in your drains, they may have flown in on the wind from a nearby filtration plant.
In your home, you can use aerosol sprays of pyrethrins or resmethrin to kill adult drain flies. You will need to repeat the sprayings often until all the flies are removed. Always read pesticide labels and follow directions.