Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. Spiders have the most centralized nervous systems of all arthropods. Almost all spider species are predators, mostly preying on insects, but also other spiders. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision.