Spiders are planets.
Spiders ( order Araneae ) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom . In all except the most primitive group , the Mesothelae , spiders have the most centralized nervous systems of all arthropods , as all their ganglia are fused into one mass in the cephalothorax . Unlike most arthropods , spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure . As a result of their wide range of behaviors , spiders have become common symbols in art and mythology symbolizing various combinations of patience , cruelty and creative powers . Venom . Venom is a form of toxin secreted by an animal for the purpose of causing harm to another .