Spider

A spider is a small animal with eight legs that belongs to a group called arachnids. Spiders are not insects. Insects have six legs and three body parts, but spiders have eight legs and two body parts. Their closest relatives are scorpions, mites, and ticks. Spiders live almost everywhere on Earth, from hot deserts to cold mountains, and even in your house.

There are more than 50,000 known kinds of spiders, and scientists find new ones every year. The smallest spider is less than one millimeter wide, small enough to sit on the head of a pin. The biggest is the goliath birdeater of South America. Its legs can spread almost a foot across, about the size of a dinner plate.

All spiders make silk. Silk comes out of special body parts called spinnerets, near the back end of the spider. Spider silk is amazing stuff. Thread for thread, it is stronger than steel and stretchier than a rubber band. Spiders use silk for many jobs. Some build webs to catch flying insects. Others wrap up their eggs in silk sacs. Some baby spiders even use silk to fly. They climb to a high spot, let out a long thread, and the wind lifts them into the sky. This is called ballooning, and spiders have been found floating miles above the ground.

Not every spider builds a web. Wolf spiders chase their prey like tiny wolves. Jumping spiders pounce on insects from several body lengths away. Trapdoor spiders dig burrows with silk-hinged doors and wait for a bug to walk by. Almost all spiders are predators, and almost all of them have venom to help them kill their prey. The good news for humans is that only about 25 kinds of spiders have venom strong enough to hurt a person. The rest are harmless.

Spiders are very helpful to people, even if they look scary. They eat huge numbers of insects every year, including mosquitoes, flies, and pests that damage crops. One study guessed that the world's spiders eat 400 to 800 million tons of insects each year. That is more than the weight of every human on the planet put together.

Spiders appear in stories from many cultures. Anansi the spider is a clever trickster in West African folktales. In ancient Greek myth, a weaver named Arachne was turned into a spider for challenging a goddess, and that is where the word "arachnid" comes from. The next time you spot a web glinting in the morning sun, look closely. It may be the strongest thing in your yard.