About House Flies

About House Flies

One of the most common domestic insect, the housefly (Musca domestica) 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. It has been suggested that this fly came originally from Africa but nowadays it has followed us to all parts of the earth. In Northern Europe it probably didn't become established until man started keeping domestic animals indoors during the winter, a practice that didn't start until about the beginning of the Iron Age, c. 400 B.C.

The housefly has a complete metamorphosis with distinct egg, larva or maggot, pupal and adult stages. The house fly overwinters in either the larval or pupal stage under manure piles or in other protected locations. Warm summer conditions are generally optimum for the development of the house fly, and it can complete its life cycle in as little as seven to ten days, and as many as 10 to 12 generations may occur in one summer. Each female fly can lay up to 500 eggs in several batches of about 75 to 150 eggs, each over a three to four day period. The number of eggs produced is a function of female size, which is principally a result of larval nutrition. The mature larva is 3 to 9 mm long, typical creamy whitish in color, cylindrical but tapering toward the head. The head contains one pair of dark hooks. The pupae are dark brown and 8 mm long. The pupal stage is passed in a pupal case formed from the last larval skin which varies in color from yellow, red, brown, to black as the pupa ages. The emerging fly escapes from the pupal case through the use of an alternately swelling and shrinking sac, called the ptilinum, on the front of its head which it uses like a pneumatic hammer. The house fly is 6 to 7 mm long, with the female usually larger than the male. The eyes are reddish and the mouth parts are sponging. The thorax bears four narrow black stripes and there is a sharp upward bend in the fourth longitudinal wing vein. The abdomen is gray or yellowish with dark midline and irregular dark markings on the sides. The underside of the male is yellowish. The sexes can be readily separated by noting the space between the eyes, which in females is almost twice as broad as in males.

Flies multiply at an enormous rate; it takes roughly two weeks from the time a female hatches until she is able to lay eggs of her own. Favourite breeding sites are horse and cow dung, exposed human feces, rotting garbage and carrion. In more developed countries, modern sewage systems, refuse removal, and general cleanliness have had a marked effect in controlling the insect's numbers. The potential reproductive capacity of flies is tremendous, but fortunately can never be realized. It has been stated that a pair of flies beginning operations in April may be progenitors, if all were to live, of 191,010,000,000,000,000,000, flies by August.

House flies visit dung, carrion, and offal of all kinds and naturally they pick up bacteria and viruses. They therefore act as carriers of diseases and are wholly undesirable from a hygienic viewpoint. More than 100 pathogens associated with the house fly may cause disease in humans and animals, including typhoid, cholera, bacillary dysentery, tuberculosis, anthrax ophthalmia and infantile diarrhea, as well as parasitic worms. Pathogenic organisms are picked up by flies from garbage, sewage and other sources of filth, and then transferred on their mouthparts and other body parts, through their vomitus, faeces and contaminated external body parts to human and animal food. In addition they can be intensely irritating when they occur in great swarms, settling on man and beast alike.

Besides being a nuisance, it is a prime carrier of disease. Its entire body swarms with millions of bacteria. Typhus, dysentery, tuberculosis, and poliomyelitis are only a few of the illnesses for which it is a carrier. General cleanliness have had a marked effect in controlling the insect's numbers. Good sanitation is the basic step in any fly management program. Food and materials on which the flies can lay eggs must be removed, destroyed as a breeding medium, or isolated from the egg-laying adult. Fly traps may be useful in some fly control programs if enough traps are used, if they are placed correctly, and if they are used both indoors and outdoors. House flies are attracted to white surfaces and to baits that give off odors. Indoors, ultraviolet light traps collect the flies inside an inverted cone or kill them with an electrocuting grid. With the increasing incidence of insecticide resistant house fly populations, rising costs of insecticides and a growing public concern about actual or potential problems associated with insecticides, interest in alternative house fly control strategies has increased. When the house fly is a mayor pest in commercial egg production facilities, the control of this insect is by the application of adulticides, or larvicides to directly or indirectly suppress adult densities. Residual wall sprays can be applied where the flies congregate. Resistance to permethrin develops more rapidly in fly populations from farms on a continuous permethrin regime than in farms in which permethrin and diclorvos have been alternated.