Overview:Be sure to get this straight: spiders are not insects, they’re arachnids. Spiders have eight legs, and insects have only six. Spiders have two body parts, a head and an abdomen, while insects have three body parts, a head, a thorax, and an abdomen. Insects have antennae, and spiders do not. Some insects sting. All spiders have fangs and venom. There are almost certainly a few spiders in the room with you right now.