Public Health Vectors and Pests

Moth Fly

Common Name Moth Fly / Drain Flies

Scientific Name Diptera: Psychodidae
Size Adult - 5mm
Colour Grey coloured fly with hairy wings - which make it look like a  moth.
Description Adults are small and very hairy, with a pair of pointed wings. They resemble small moths because they hold their wings roof-like over the body when at rest. They are weak fliers and appear to hop or jump.
Habitat Larvae have chewing mouthparts. Drain flies are common around sink drains, sewage treatment facilities, storm drains, dung and rotten vegetation. Larvae are aquatic or semi-aquatic, feeding on bacteria, fungi, algae and other microorganisms present in decaying organic matter. They often feed in the liquid or slime layers which develop around debris in drains, sewage treatment beds and standing water. However, when food is scarce they may become cannibalistic. Larvae are capable of surviving temperature extremes and habitats low in oxygen.
  • Eggs, laid by females hatch into pale-colored larvae. Following a feeding period, larvae pupate and soon emerge as adult flies. Adults live only 3 to 4 days without food, but they can survive for weeks if nectar or other liquid carbo-hydrate food sources are available
  • Moth flies lay eggs in a mass of 30 to 100 which hatch in less than 48 hours.
  • The larval stage lasts from 9 to 15 days and the pupal stage lasts from 20 to 40 hours.
  • Adult flies may live about 3 weeks.
Disease Transmitted 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.
  • Control of moth flies requires locating and eliminating larval breeding sites. This may be very difficult to do; perseverance and imagination will be required. One way to check individual drains as possible breeding sites is to cover the drain with a plastic film taped to the floor or fixture (e.g. a clear plastic bag). If the flies are breeding in that drain they will accumulate underneath the film within a day or two.
  • The only effective method to eliminate drain flies developing in drains is to clean the inside of the drain pipe to eliminate the organic matter. Clean slow-moving drains with a stiff brush or other tool. Drains that cannot be scrubbed can be rinsed with water under high pressure or "sterilized" by slowly pouring boiling water down along the sides of the drain pipe. Another possibility is the use of a bacterial drain treatment that biodegrades the organic matter. Follow label directions carefully for best results.
  • There is no benefit to treating drains with bleach or ammonia. Household insecticides can be used to control the adult flies, but this treatment will provide only very temporary benefit unless the source of the larvae is also removed.

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