Spiders are not insects as many people believe. They belong to a class of animals called arachnids(蛛形纲动物). Spiders have eight eyes, four pairs of legs, and can grow a new leg if they lose one. A spider's body is divided into two sections: the abdomen(腹部) and the thorax(胸部).The legs, eyes, and mouthparts are in the thorax section.

    Most spiders have poison glands(毒腺)and sharp teeth. They use their sharp teeth to force poison into the insects they catch for food. This poison can make an insect lose the ability to move, and the helpless insect is then devoured by the spider.

    Spiders usually have silk glands under their abdomen. They produce a liquid(液体)that is thicker than water from their glands. When the liquid comes into the air, it dries into silk. Many spiders use this silk to form webs to catch insects and to make cocoons(茧)that protect their eggs. This amazing silk is also used to create lines that spiders hang onto as they travel to new areas.

    Spiders live in almost everywhere on earth. The only places where there are no spiders are the coldest places, the highest mountains and the seas.