Filter Flies (drisophila species)
Filter Flies are a common nuisance in and around homes and commercial buildings, including sewage treatment plants. Adult flies may become so numerous indoors that they congregate at windows, around light fixtures, and around showers, bathtubs, sinks and floor drains. They can annoy people sitting indoors or outdoors. Since these flies often originate in unsanitary conditions, there is the possibility of disease transmission that can affect human health.
Adult filter flies are small (1/6 to 1/5 inch long), fuzzy, dark coloured insects with the body and wings densely covered with hairs. Their wings appear large for their body, are held roof-like over the body when at rest, giving them a moth-like appearance. They are weak fliers and fly only a few feet at a time. Larvae are legless, about 3/8 inch long, wormlike and grey, with both ends somewhat darker.
Life Cycle and Habits
Filter flies breed in polluted, shallow water or highly moist organic solids. You will find the eggs, larvae and pupae in the muck, slime, or gelatinous film often accumulating on the sides of drains and condensation pipes for air conditioning systems, in the sewage filtration tanks, septic tanks and moist compost. Other breeding sites include dirty rubbish containers, rain barrels and tree holes or in low lying areas adjacent to buildings where storm water collects and algae or mould grows. The female flies deposit laid eggs in irregular masses of 10 to 200 directly in and on moist organic debris. These eggs usually hatch in less than 2 days and the larvae feed on the decaying organic matter, micro organisms, algae and sediment in the debris and mature in 9 to 15 days. Larvae pupate in and on the surface of this material and new adults emerge in 1 to 2 days.
Eradicating Filter Fly Problems Non-Chemical Control
The key to solving a filter fly problem is to find and eliminate the source, i.e., find the areas of excess moisture and a build up of organic debris.