It is the most common of all domestic flies, one of the most widely distributed insects, found all over the world; it is considered a pest that can carry serious diseases.The adults are 8–12 mm long. Their thorax is gray, with four longitudinal dark lines on the back. The whole body is covered with hair-like projections. The females are slightly larger than the males, and have a much larger space between their red compound eyes. The mass of pupae can range from about 8 to 20 mg under different conditions.
Accounting for about 91% of all flies in human habitations.
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 those causing typhoid, cholera, salmonellosis, bacillary dysentery, tuberculosis, anthrax, ophthalmia, and parasitic worms. Some strains have become immune to most common insecticides.