Houseflies are the most common of all domestic flies, accounting for about 90% of all flies in that live in human habitations, and are one of the most widely distributed insects, as they are found all over the world. Flies are considered pests that can carry serious diseases.
Adult flies are 8–12 mm long and their entire body is covered with hair-like projections. The females are generally larger than the males, and have a bigger space between their eyes. Houseflies have only one pair of real wings, as the hind pair simply aids in flight stability.
Houseflies feed on feces, open sores, sputum, and moist decaying organic matter such as spoiled food, eggs and flesh. Houseflies can take in only liquid foods. Therefore, they often spit out saliva on solid foods to pre-digest it, and they then suck it back in. They also regurgitate partly digested matter and eat it again.
In cold climates, houseflies survive only with humans. They have a tendency to aggregate and are difficult to get rid of. They are capable of carrying over 100 pathogens, such as typhoid, cholera, Salmonella,bacillary dysentery, tuberculosis, anthrax, ophthalmia, and parasitic worms. The flies in poorer and lower-hygienic areas generally carry more pathogens. Some strains have become immune to most common insecticides.
Houseflies have a high intake of food, therefore they deposit feces constantly, which is just one of the factors that makes the insect a dangerous carrier of diseases. Although they are domestic flies usually confined to the human habitations, they can fly for several miles from the central breeding place. Houseflies are active only in daytime and rest at night (sometimes at the corners of rooms, ceiling hangings, etc.)