Adult flies normally live for 2 to 4 weeks but can hibernate during the winter. The adults feed on a variety of liquid or semi-liquid substances and solid materials which have been softened by saliva. They carry pathogens on their bodies and in their feces and can contaminate food and contribute to the transfer of food-borne illnesses. Because of their large intake of food they deposit feces constantly, which makes flies a dangerous carrier of disease.
Although they are domestic flies, usually confined to human habitations, they can fly for several miles from the breeding place. They are active only in daytime, and rest at night in the corners of rooms, ceiling hangings and basements where they can survive the coldest winters by hibernation.
The female housefly usually only mates once and stores the sperm for later use. She lays batches of about 100 eggs on decaying organic matter such as garbage, carrion or feces. These soon hatch into legless white maggots which after 2 to 5 days and transform into reddish-brown pupae.