The housefly (also house fly, house-fly or common housefly), Musca domestica, is the most common of all flies fluttering in homes, and indeed one of the most widely distributed insects; it is often considered a pest that can carry serious diseases.
The adults are 6-9 mm long. Their thorax is gray, with four longitudinal dark lines on the back. The underside of their abdomen is yellow, and their whole body is covered with hair. The females are slightly larger than the males, and have a much larger space between their red compound eyes.
Like most Diptera (meaning "two-winged"), houseflies have only one pair of wings; the hind pair is reduced to small halteres that aid in flight stability. Characteristically, the media vein (M1+2 or fourth long vein of the wing) shows a sharp upward bend.
House flies tend to stay within 1-2 miles of where they were born; however, they have been known to migrate up to 20 miles to find food.
In colder climates, houseflies survive only with humans. They have a tendency to aggregate and are difficult to dispel. 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 usually carry more pathogens.