Everyone is familiar with house flies. Common household pests, they visit dumps, sewers and garbage heaps, feeding on fecal matter, discharges from wounds and sores, sputum, and all sorts of moist, decaying matter such as spoiled fish, eggs and meat. Flies regurgitate and excrete wherever they come to rest and thereby are ideally suited to mechanically transmit disease organisms. House flies are suspected of transmitting at least 65 diseases to humans.

Description:

House flies are gray, approximately 6 mm (1/4 inch) long, with four dark longitudinal stripes on top of the thorax, or middle body region. The mouth parts of the house fly are adapted for sponging up liquids. They cannot bite. Flies ingest only liquid food; they feed on solid food by regurgitating saliva onto it. The saliva liquefies the solid material, which is then sponged up with the proboscis. They require water since they continually salivate. Fly specks seen on surfaces visited by house flies are the excreted wastes.

Life Cycle:

Female house flies deposit their eggs in decaying organic matter such as garbage and human and animal excrement. Horse manure is the preferred breeding medium. Each female deposits about 100-150 eggs on appropriate food. Eggs hatch in a day or two into worm-like creatures called maggots. Maggots lack definite heads, eyes, antennae and legs. Their bodies are pointed at the front end and gradually widen at the rear. Fly maggots feed on the material in which they have hatched. Following three larval molts, mature larvae stop feeding and burrow into drier surrounding areas, where they pupate. The pupa is a chestnut-brown, oval object within which the larva changes into an adult house fly. Adults mate within one to two days after emerging from their pupal cases. The life cycle from egg to adult can be completed in as little as one week, but typically takes three weeks. House fly adults normally live about two and a half weeks during the summer, but they can survive up to three months at lower temperatures. Some overwinter outdoors in protected locations, or in crevices in buildings. Flies normally stay within one or two miles of their point of origin, but some have been known to travel as far as twenty miles.

Control:

The three basic principles of house fly control are sanitation, exclusion and non-chemical measures. Sanitation will provide the best long-term control, followed by exclusion and non-chemical measures, which provide shorter-term management.

Sanitation: Flies can't breed in large numbers if food sources are limited. Don't allow materials such as manure, garbage or other decaying organic matter to accumulate. Keep trash cans clean and tightly covered. If garbage becomes infested with maggots, dispose of it immediately.

Exclusion: Flies can be kept outside of homes by the use of window and door screens. Make sure screens are tight fitting and without holes. Keep doors closed, making sure there are no openings at the top or bottom. Check for openings around water or gas pipes or electrical conduits that feed into the building. Caulk or plug any openings. Ventilation holes should be screened, as they can serve as entryways for flies as well.

Non-chemical Measures: The use of devices such as ultraviolet-light traps, sticky fly traps, fly swatters, and baited fly traps can eliminate many flies inside a home, but the fly swatter is the most economical control method for the occasional fly.

Adapted from Dewey M. Caron, University of Delaware, 1999