The Average Life Span of a Fly

Unless you live on a polar ice cap, you will deal with flies. More than 16,000 species of flies inhabit North America, and just a pair of flies that survives winter ensures they'll live on to torment you. A pair of flies and their offspring can produce more than 1,000,000 offspring in a matter of weeks. Hundreds of millions microorganisms live in and on the fly, and every time he lands on something -- which is frequently -- he deposits bacteria.

No matter what kind of fly is bothering you, he has to go through a four-stage life cycle. A fly begins as an egg and hatches into a larva -- or maggot -- often within 24 hours of being fertilized. The amount of time it takes the larva to develop into a pupa can take several days or several weeks, depending on the surrounding temperature and availability of food. In the pupal stage, the insect transforms from legless larva into a fly; again, the temperature affects whether his transformation is a quick few days or a few weeks.

Just about everyone has experienced the house fly, which potentially carries more than 100 disease-causing germs, including Salmonella and E. coli. The larva of a house fly grows fastest above 95 degrees Fahrenheit, but the optimal survival temperature is between 62 and 90 degrees. It takes four to 13 days for him to reach the pupal stage at this temperature. The pupal stage will last a few days if the temperature is above 90 degrees; at 57 degrees, he'll need between two and four weeks to reach adulthood. Once he's left the pupal stage, he can expect to live between 15 and 25 days, but he can make it to two months. If he doesn't quickly find food, however, he'll last only a couple or three days. He thrives with foods high in sugar and in temperatures between 75 and 80 degrees Fahrenheit.

Every bit as annoying as the house fly, the fruit fly is smaller and has a shorter adult life span. It takes just over a day for the fruit fly egg to hatch. He'll spend about a week in the larval stage and a week in the pupal stage, becoming an adult about two weeks after he's hatched. He can expect to live between eight and 10 days, though some fruit flies last as long as a month. Decaying fruits and vegetables do double duty for him; he feeds on them the females will lay eggs on them. Any moist, decaying or fermenting material is a breeding option for the fruit fly, including drains, empty bottles, mops and cleaning rags. Though he's primarily a nuisance, this insect also carries bacteria he picks up on his travels.

If flies are annoying you, the best offense -- aside from a flyswatter -- is cleanliness. Eat, refrigerate or discard ripe produce. Don't allow trash and clutter to sit around to entice pests. Keep your kitchen counters clean and free of morsels that flies find appealing.