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
Diania as the armoured Lobopodia. These have long been assumed to be related in some way to Arthropoda and it seems likely that arthropods evolved from somewhere within this group. However, all previously discovered lobopodians showed soft, rather ring-like, but not segmented legs. The significance of "Diania" is that it is a lobopodian which appears to have evolved the name-giving character of the arthropods: jointed legs. In the original description of the fossil the authors suggested that "Diania" could be the sister group of "Schinderhannes" and the remaining arthropods, but discussed the possibility that it may be a more primitive form