The housefly (Musca domestica Linnaeus) is the most common fly occurring in homes and indeed one of the most widely distributed animals and the most familiar of all flies; it is a pest that can facilitate serious diseases.
The adults are 5-8 mm long. Their thorax is greyish, with four dark longitudinal lines on the back. The underside of the abdomen is yellowish. The whole body is covered with hair. They have reddish compound eyes. The females are slightly larger than the males and have a much larger space between the eyes. Like most Diptera, houseflies have only one pair of wings; the second pair is reduced to small halteres that aid in flight stability.
Each female fly can lay up to 500 eggs (in five patches of 100 eggs each). Within a day, the larvae (maggots) hatch from the eggs; they live and feed in (usually dead and decaying) organic material, such as garbage or feces. They are pale whitish and have no legs. After several molts, the maggots crawl to a dry cool place and transform into pupae, colored reddish or brown. The adult flies then emerge from the pupae. (This whole cycle is known as complete metamorphosis.) The adults live from half a month to a month. After having emerged from the pupae, the flies don't grow anymore. Small flies are not young flies but the result of little food during the maggot stage.
Some 36 hours after having emerged from the pupa, the female is receptive for mating. The male mounts her from the back to inject sperm. Normally the female mates only once, storing the sperm to use it repeatedly for several sets of eggs. Males are territorial: they defend a certain territory against other males and try to mount any female that enters.
Some species of wasps can parasitize and kill the pupae.
Houseflies can only take in liquid foods. They spit out saliva on solid foods to pre-digest it, and then suck it back in. They also throw up partially digested matter and eat it again.
The flies can walk on vertical planes (http://www.straightdope.com/classics/a5_043.html), and can even hang upside down from ceilings. This is accomplished with the surface tension of liquids secreted by glands near their feet.
Lacking eyelids, the flies continually clean their eyes with their forelegs. Most of their taste and smell sensor cells are on hairs on their legs, and that is why they also keep rubbing their legs together (http://www.straightdope.com/classics/a940204.html) (<<- the untold story).
Two copulating houseflies
Houseflies originated in Africa; it is quite possible that they entered America along with Christopher Columbus. They depend on warm temperatures; generally, the warmer the temperature the faster the flies will develop. In colder climates, houseflies only occur together with humans. In the winter, most of them survive in the larval or pupa stage in some protected warm location.
Flies have a tendency to aggregate and are difficult to dispel, causing great annoyance to humans. They are capable of carrying over 100 pathogens, such as typhoid, cholera, Salmonella, bacillary dysentery, tuberculosis, anthrax ophthalmia, and parasitic worms. Some strands have become immune to common insecticides.
- House Fly (http://creatures.ifas.ufl.edu/urban/flies/house_fly.htm) from the University of Florida
- Many annotated images (http://icb.usp.br/~marcelcp/Muscadomestica.htm)
- Article on housefly (http://www.hydeparkmedia.com/housefly.html), from Chicago Tribune
- Articles and Pictures (http://www.fly-kill.co.uk/pages/info_fly.htm)
- If I hadn't killed 52 flies as a child, how many descendants would they have had by now? (http://www.straightdope.com/classics/a1_022.html) courtesy of The Straight Dope (http://www.straightdope.com/index.html)