The common housefly is an interesting insect. It has four stages of development, and in each stage, it looks completely different. The average lifespan of the housefly is 15 to 30 days. They can multiple rapidly given their short lifespan, and carry more than 100 diseases, including cholera and tuberculosis.
Houseflies begin life as eggs. The female housefly can lay up to 500 eggs at one time, though she deposits each egg individually. The ideal incubation location for a housefly egg is in something warm and moist, such as manure. The eggs are about 0.12 cms in size and white, resembling grains of rice. The eggs gestate for 24 hours before the flies hatch.
Once the egg hatches, the housefly emerges in its larval stage. It is also known as a maggot at this point. The maggot looks like a legless worm, with a pointed end (the mouth) and two spiracles (breathing holes) at the back end. Maggots eat continuously over a period of four to five days. Before their metamorphosis into the next stage of development, the maggots migrate to a drier, darker location.
At the start of the pupal stage, the fly is approximately 8 mms long. As the pupa ages, the pupal skin will change colors from yellow to red to brown, and then black. If temperature is optimal, the pupa matures in two to six days, though it can take up to 17 days in colder climates.
When the housefly emerges from the pupal stage, it has attained full maturity and now looks like a fly. The adult housefly is ready to reproduce within five days of maturity. Adult houseflies can only eat liquids, so they secrete their saliva onto food and suck it up with their proboscis. Adult houseflies can contaminate food with the myriad diseases they carry by touching it with their mouth parts, which retain the germs picked up from manure, sewage and other food sources.
Most houseflies die within one month of maturing from the pupal stage. They can die from cold, lack of food and old age. Humans can assist the process by application of insecticides and fly strips. To manage fly infestation, cover open sources of excrement or rotting vegetables, such as animal housing or compost bins. Killing adult flies will not eliminate the source of contamination unless you remove any viable breeding grounds for the flies. For smaller infestations, boric acid sprinkled near preferred breeding areas is an effective way to control fly populations without using harsher chemicals.