Heather Lehman, age 9, of Willingboro, N.J., for her question:
HOW LONG DOES A HOUSEFLY LIVE?
A fly is an insect with two wings. There are about 100,000 different kinds of flies but the common housefly is one of the best known. The common housefly usually lives about 30 days during the warm months of summer.
A female fly will lay from one to 250 eggs at a time, depending on the species. During her lifetime, a single female may lay as many as 1,000 eggs.
At the tip of a female fly's abdomen is an organ called the ovipositor, with which the eggs are laid. The housefly usually pushes her ovipositor into soft masses of decaying plant or animal material and lays her eggs there.
A housefly's eggs hatch in eight to 30 hours, but the time depends on the species of the fly. There are then three or more stages of a fly's cycle: the larva, a pupa and finally an adult.
Larava of a fly is often called a maggot or a wriggler. The larvae of most kinds of flies look like worms or small caterpillars. They live on food, garbage, sewage, soil, water and on living or dead plants and animals.
A fly larva spends all of its time eating and growing. Several times it molts or sheds its shell and grows a new one.
The pupa is the stage of final growth before a fly becomes an adult. The pupae live on land and remain quiet. The larvae build a strong oval shaped case called a puparium around their bodies. Inside the puparium, the larva gradually loses its wormlike look as it takes on the shape of an adult fly.
After the change is complete, the adult fly bursts one end of the puparium or splits it down the back and crawls out.
The pupal stage of a housefly lasts from three to six days in hot weather and longer in cool weather.
When the adult housefly leaves the puparium, its wings are still moist and soft. The air dries the wings quickly and blood flows into the wing veins and stiffens them. The thin wing tissue hardens in a few hours, and then within a few days the adult flies away to find a mate.
The fly has reached its full size when it comes out of the puparium. The housefly grows no larger as it gets older, even though its abdomen may swell with food or eggs.
Most adult flies die when the weather gets cool at the end of summer. Many of the larvae and pupae stay alive during the winter months and as soon as the warm weather returns, a new crop of houseflies is born.
A fly's wings are so thin that the veins show through. The veins not only carry blood to the wings but also help stiffen and support them. Instead of hind wings, a fly has a pair of thick, rodlike parts with knobs at the tips. These parts, called halters, give the fly its sense of balance. They vibrate at the same rate as the wings when the insect is flying.
A housefly's wings beat at about 200 times a second and it will fly at a speed of 4 1/2 miles per hour.