Spider behavior Spider behavior Spider behavior refers to the range of behaviors and activities performed by spiders. Spiders are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms which is reflected in their large diversity of behavior. Almost all known spider species are predators, mostly preying on insects and on other spiders, although a few species also take vertebrates such as frogs, lizards, fish, and even birds and bats. Spiders' guts are too narrow to take solids, and
Sea spider insects or crustaceans. This is in dispute, however, as genetic evidence suggests they may be the sister group to all other living arthropods. Sea spiders have long legs in contrast to a small body size. The number of walking legs is usually eight (four pairs), but species with five and six pairs exist. Because of their small size and thin body and legs, no respiratory system is necessary, with gases moving by diffusion. A proboscis allows them to suck nutrients from soft-bodied invertebrates, and their digestive tract has diverticula extending into the legs. Certain Pycnogonids are so small that each