Spiders are arachnids. Arachnids are a class of animals with eight legs, two-part bodies (the head and the abdomen) and no wings or antennae. They come in a variety of sizes and colors. Almost all spiders are venomous, but while some bites are fatal to humans, others may cause no reaction at all. Spiders are carnivores, which means they eat other insects and animals. Some spiders weave webs to catch their prey -- like the character Charlotte in "Charlotte's Web" -- while others do not weave.
While almost all spiders are venomous, in the majority of cases, the venom is not capable of causing harm to humans. Spiders use venom to paralyze their prey before eating it. In some cases, their venom is strong enough to kill their prey. They also use venom to ward off predators. The two most common spiders in the United States with venom strong enough to be fatal to humans are the brown recluse and the black widow.
Spinning and Weaving
All spiders produce silk, but not all spiders weave webs. The silk, which is very strong, is released from glands in their abdomens. Spiders use the silk to climb, travel by swinging, build egg sacs and create webs to catch and subdue their prey. Spiders weave different kinds of webs. There are spiral, or orb, webs that form a circular pattern. Cobwebs are woven in a tangled pattern. There are also sheet, funnel and tubular webs.
Types of Spiders
According to Explorit Science Center, there are 35,000 kinds of spiders worldwide that have been given distinct names, but there are many more than that haven't been identified by scientists yet. Three thousand of these named spiders live in the Untied States. Jumping spiders are the largest family of spiders. They are small, brightly colored and leap distances up to 40 times their size. Other families of spiders in the U.S. include: orb weavers, funnel weavers, cobweb spiders, wolf spider, nursery web spiders and crab spiders.
Tarantulas are the largest spider and the most common variety to be kept as pets. While their size and furry bodies can make them seem scary, they are generally harmless, though the bites of some varieties can cause pain and swelling. Caution should be used when handling them. Tarantulas' bodies range from 1 to 4 inches long with 3- to 12-inch leg spans. They do not weave webs but mainly eat insects.