Everybody knows house flies. As common household pests, they frequent 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 animal meat. Flies regurgitate and excrete whenever they come to rest and are hence ideal transmitters of disease and other bacterial and viral organisms. House flies are suspected of transmitting a minimum of 65 diseases among humans.
House flies are usually gray, on average 6 mm (1/4 inch) in size, with four dark longitudinal stripes on top of the thorax, or middle body region. The mouth of the house fly is well adapted for sponging liquids. They do not bite. Flies ingest only liquids and feed on solid food by regurgitating saliva onto it. The saliva liquefies solid material, which then is sponged up using the proboscis. Flies require water because they salivate nearly constantly. Fly specks seen on surfaces visited by house flies are excreted waste.
Female house flies lay their eggs in decaying organic matter like garbage and/or in or on human or other animal excrement. Horse manure is a preferred breeding area. Each female deposits between 100 and 150 eggs on appropriate food. Eggs hatch in a day or two into the little worms we all know as maggots. Maggots do not have defined heads, eyes, antennae or legs. Their bodies are pointed at the front and gradually widen toward the rear. Fly maggots feed on whatever material they were hatched. Following three larval molts, mature larvae stop feeding and burrow finding more dry places in surrounding areas. This is when they pupate. The pupa is a chestnut-brown, oval “egg” in which the larva changes into an adult house fly. Adults mate within one to two days after pupating. The life cycle from egg to adult can be completed in a week, but usually takes closer to three weeks. House fly adults live approximately two and a half weeks, during the summer, but can survive up to three months at lower temperatures. Some even winter outdoors in protected locations like crevices of buildings. Flies normally stay no further than one or two miles of their point of origin, but some have been found to travel up to twenty miles.