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's a pest that carries and transmits serious diseases. Physical description The adults are 6-9 mm long. Their thorax is gray, with four dark 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 male… (More on Housefly)