Locomotion Spider

image of spider leg: 1–coxa; 2–trochanter; 3–femur; 4–patella; 5–tibia; 6–metatarsus; 7–tarsus; 8–claws

each of 8 legs of spider consists of 7 distinct parts. part closest , attaching leg cephalothorax coxa; next segment short trochanter works hinge following long segment, femur; next spider s knee, patella, acts hinge tibia; metatarsus next, , connects tibia tarsus (which may thought of foot of sorts); tarsus ends in claw made of either 2 or 3 points, depending on family spider belongs. although arthropods use muscles attached inside of exoskeleton flex limbs, spiders , few other groups still use hydraulic pressure extend them, system inherited pre-arthropod ancestors. extensor muscles in spider legs located in 3 hip joints (bordering coxa , trochanter). result, spider punctured cephalothorax cannot extend legs, , legs of dead spiders curl up. spiders can generate pressures 8 times resting level extend legs, , jumping spiders can jump 50 times own length increasing blood pressure in third or fourth pair of legs. although larger spiders use hydraulics straighten legs, unlike smaller jumping spiders depend on flexor muscles generate propulsive force jumps.

most spiders hunt actively, rather relying on webs, have dense tufts of fine hairs between paired claws @ tips of legs. these tufts, known scopulae, consist of bristles ends split many 1,000 branches, , enable spiders scopulae walk vertical glass , upside down on ceilings. appears scopulae grip contact extremely thin layers of water on surfaces. spiders, other arachnids, keep @ least 4 legs on surface while walking or running.