All spiders have eight legs. Spiders also possess a pair of shorter limbs called the pedipalps, that in males serve as sex organs. Spider legs contain seven distinct segments.
The pedipalps contain only six segments, are located on the head before the first pair of legs, and are used as sensory organs. The true legs end in either two or three claws; web-making spiders use the third claw to grip strands of web as they walk across the structure. Hunting spiders have tufts of hair in between their claws that allow them to attach to moist surfaces and walk up walls. Spider legs are unique in that although they do contain muscle, spiders use the hydraulic pressure of bodily fluid to extend them. Muscles are only used to flex.