Spiders are invertebrates. That means they do not have backbones. They have exoskeletons. The exoskeleton is a hard covering on the outside of the body. Spiders are also arachnids. That means they have eight legs. They have no wings or antennae.

Spider bodies have two sections. The front one is called the cephalothorax. The back section is the abdomen. These are connected by a tiny tube called the pedicel. This tube is flexible. It allows the back of the spider to move without moving the front.

A spider’s eight legs are attached to the front section. Most, but not all, spiders have eight eyes.

The spider’s mouth is in the front. Instead of jaws, it has two little legs behind its mouth. These are called pedipalps. The pedipalps are used to hold on to prey. A spider also has two even smaller legs in front of its mouth. Each one has a fang. Most spiders use fangs to inject venom into prey. The venom stuns or kills the prey. It also dissolves the prey. Then the spider can drink its food. Almost all spiders have venom. Most spider venom does not hurt humans.

Spiders have spinnerets on their abdomens. These are used to spin silk. Not all spiders spin webs, but they all use silk for something.

One kind of tarantula is as big as a dinner plate. The mygalomorph spider is as small as a pinhead. There are about 40,000 spider species.