TECHNICAL DATA SHEET
Filter, Drain flies or Owl Midges (Psychoda spp)
Identification:
Tiny flies up to 2mm long. Light grey or tan body with lighter coloured hairy wings held roof-likeover the body, which give the body a fuzzy appearance.
Origins and distribution: Worldwide and endemic throughout the UK.
Habitat:
Common in effluent plants and filter beds where they are often encouraged as they help in the breaking down process of matter fed in these beds.
Behaviour:
They are poor fliers and commonly seen walking or running on walls and other resting surfaces.
When they do fly the flight covers a few feet and is in short jerky lines which is characteristic of these flies. During the day, the adults rest in shaded areas on walls near plumbing fixtures or on the side of tubs and showers. Most of their activity occurs during the evening when they may be seen hovering about drains and sinks.
Breeding:
200 eggs laid in batches on decaying and wet matter, particularly in drains,gullies or where sludge has been allowed to accumulate. Larvae live in this matter feeding until pupation. They have a siphon at the end of their bodies, which sometimes is seen breaking the surface film. The eggs take 1-6 days to hatch; the larvae grow from 1 mm to 9mm and develop from 10-50 days according to temperature. There can be as many as 8 generations per year.
Food:
Decaying and wet matter, of algae, fungal and bacterial nature particularly in drains, gullies or where sludge has been allowed to accumulate. The sludge is broken down into tiny faecal pellets.
Control:
Control can be achieved by improved drain and gully hygiene, look for a blocked drain, gully or grease trap. Toilets and sanitary bins are also sometimes the attraction, ensure they are clean.
ULV fogging treatments will eradicate the adult population, until the next generation arrives.
Most species can penetrate through ordinary Fly screening although a finer mesh is available.
Glue board style Ultra violet fly killers can be effective as the first line in defence. With normal fly killers they are so small they do not get electrocuted. This fly is sometimes wrongly confused with the fruit fly.