A spider is not an insect. Spiders are arachnids. A spider has eight legs and two body parts, and an insect has three body parts. Most spiders have eight eyes, though some have fewer.

Most spiders eat insects. Spiders in gardens eat many kinds of insects, including pests. A 2017 study estimated that all the spiders in the world together eat 400 to 800 million metric tons of prey a year. More than 90 percent of it is insects and springtails.

The researchers said all people together eat about 400 million tons of meat and fish a year. That is the low end of the spiders' estimated 400 to 800 million tons of prey.

Every kind of spider makes silk with spinnerets. Spider silk is very light, but it is also extremely strong and flexible. Many spiders catch flies and other insects in their webs. A spider web has sticky threads and nonstick threads, and the spider knows which threads are safe to walk on.

An orb web has radial threads that make the frame and a spiral thread that catches prey. Orb-weaving spiders often eat their old silk and reuse it.

Not every spider builds a web. Some hunt for prey or wait for it. Wolf spiders are hunting spiders, and they do not build webs to catch prey.

Spiders cannot chew solid food. They put digestive fluids into their prey. A spider's mouth is shaped like a tiny drinking straw and sucks rather than chews. Spiders use venom to paralyze the small animals they catch. After catching an insect, a spider wraps it in silk.

Most spiders are harmless to people. Spiders very rarely bite people, and they do not seek people out to bite them. Do not touch a wild spider. If you see one, tell a grown-up.

Words to know

• arachnids: spider group
• spinnerets: silk makers
• venom: spider poison
• digestive: breaking down food