The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food. The upper surface of the cephalothorax is covered by a single, convex carapace , while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive Mesothelae , whose living members are the Liphistiidae , have segmented plates on the upper surface. Its place is largely taken by a hemocoel , a cavity that runs most of the length of the body and through which blood flows.
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Distinguishing characteristics[ edit ] Note the difference in the orientations of the chelicerae fangs of the two spiders below, representatives of the Mygalomorphae and the Araneomorphae. The number of book-lungs when present can also help distinguish between members of these two major groups. Araneomorphae[ edit ] In the Araneomorphae, the fangs slope towards each other, giving these spiders many more possibilities than the Mygalomorphae, which can only bite top down. In contrast to the Mygalomorphae, where females can live for many years, most Araneomorphae die after about a year.
The major exception is the Tarantulas , which have become so common as pets that many people have seen them. There are a few other members of Mygalomorphae that one might see around homes or gardens, but they typically are relatively small and not easily noticed.
For instance, the females of one such species lives and hunts from within a long silken tube, so unless one opens the tube or chances upon a male looking for a mate, one will never see them.
The Araneomorphae, to the contrary, include the weavers of spiral webs , the cobweb spiders that live in the corners of our rooms and between windows and screens, the crab spiders that lurk on the surfaces of the flowers in our gardens, the jumping spiders that look back at us curiously from walls and tree trunks, the wolf spiders that sometimes carpet good hunting sites in a sunny spot in the lawn, the large Huntsman spiders that sometimes frighten people by getting into their cars or taking up residence behind wall clocks.
Atrax robustus Systematics[ edit ] In older schemes, the Araneomorphae are divided into two lineages, the Hypochilae containing only the family Hypochilidae , and the Neocribellatae. The Neocribellatae are in turn divided into the Austrochiloidea, and the two series Entelogynae and Haplogynae, each containing several superfamilies : A cladogram shows the relation among taxa: .
Ecology of the True Spiders (Araneomorphae)