Todd Pferman, age 14, of Grand Forks, N.D., for his question:
HOW DO SPIDERS MATE?
As soon as a male spider reaches maturity, he seeks a mate. Most male spiders perform courtship activities that identify themselves and attract the females. The male of some species vibrates the threads of the female's web. Some male hunting spiders wave their legs and bodies in an unusual courtship dance.
Sometimes the female spider may mistake the male for prey and eat him.
Before mating, a male spider spins a silk platform. He deposits a drop of sperm from his abdomen onto the platform. Then he fills each of his pedipalpi with sperm and mates.
Pedipalpi are a pair of appendages that look like small legs. One pedipaip is attached to each side of the spider's mount and they form the sides of the mouth opening. Each pedipalp has six segments or parts. In most kinds of spiders, the segment closest to the body bears a sharp plate with jagged edges. The spider uses this plate to cut and crush its food. In male spiders, the last segment of each pedipalp bears a reproductive organ.
After mating, the female stores the sperm in her body. When she lays her eggs, several weeks or even several months later, the eggs are fertilized by the sperm.
The number of eggs a spider lays at one time varies with the size of the animal. A female of average size lays about 100 eggs. Some of the largest spiders lay more than 2,000 eggs. One tiny female cave spider lays one egg at a time.
In most species, the mother spider encloses the eggs in a silken egg sac. The sac of each species differs in size and shape. Some species that lay large numbers of eggs make several sacs and some spin them together into long chains.
In many species, the mother dies soon after making the egg sac. In other species, she stays with her eggs until they hatch. Some spiders hang the sack in a web. Others attach the sac to leaves or plants. Still others carry it with them.
Spiderlings hatch inside the egg sac and remain there until warm weather arrives. If the eggs are laid in autumn, the spiderlings stay quietly inside their egg sac until spring.
After leaving the egg sac, the spiderlings immediately begin spinning draglines.
Many spiderlings travel to other areas. To do this, a spiderling climbs to the top of a fence post or some other tall object and tilts its spinnerets up in the air. The moving air pulls silk threads out of the spinnerets. Then the wind catches the threads and carries the spiderling into the air like a balloon on a string.
This unusual way of traveling is called ballooning. Sailors more than 200 miles from land have seen ballooning spiders floating through the air.
Spiderlings molt or shed their outer skin several times while they are growing. A new, larger skin replaces the old skin that has grown too tight. Most kinds of spiders molt from five to nine times before they reach adulthood.