Ronda Rethwill, age 8, of Eugene, Ore., for her question:
HOW DOES A FLY REPRODUCE?
Flies can be found throughout the world. There are about 100,000 different kinds of the insects including the common housefly, horseflies, gnats, deer flies, fruit flies, mosquitoes and tsetse flies. Flies have two wings and many are considered by many scientists to be man's most dangerous pests. Often they carry germs either on or inside their bodies.
A female fly will lay somewhere between one and 250 eggs at a time, depending on the species. She may be able to lay up to 1,000 during her lifetime.
At the tip of a female fly's abdomen you'll find an organ called the ovipositor. It is through this organ that the fly will lay her eggs, dropping them either on the water, on the ground or on animals.
A common housefly will usually push her ovipositor into a lump of decaying plant or animal material and lay her eggs there.
The eggs of many flies are white or pale yellow and look like tiny grains of rice.
Within eight to 30 hours after the common housefly has laid her eggs, they will hatch. From the egg, the fly will pass through a larva and pupa stage before becoming an adult.
A larva, which is often called a maggot or a wriggler, hatches from the egg. It looks very much like a worm or small caterpillar and it lives in food, garbage, sewage, soil, water or in living or dead plants and animals.
The fly larva spends all of its time growing and eating. It sheds its shell several times as it grows. This larva stage can last from a few days to two years, depending on the species. From the larva, the fly then turns into a pupa.
The pupa stage of a housefly lasts from three to six days. The insect grows inside a cocoon like strong, oval shaped case that the larva builds around its body. After a change, one end of the puparium, as the case is called, splits open and out crawls an adult fly.
When the fly leaves the puparium, its wings are still moist and soft but air dries them quickly and blood flows into the veins making the wings stiff. The thin wing tissue hardens in a few hours and the fly is on its way to find a mate.
A fly is full size when it comes out of its puparium. As it grows older, its abdomen may swell with food or eggs, but the wings and rest of the body remain the same size.
An adult housefly will live about 30 days in summer. Most adult flies die when the weather gets cold, but many larvae and pupae stay alive during the winter and develop into adults in the spring.