Solifugae many species also are used for stridulation. Unlike scorpions, solifugids do not have a third tagma that forms a "tail". Most species of Solifugae live in dry climates and feed opportunistically on ground-dwelling arthropods and other small animals. The largest species grow to a length of , including legs. A number of urban legends exaggerate the size and speed of the Solifugae, and their potential danger to humans, which is negligible. Solifugae are moderately small to large arachnids (a few millimeters to several centimeters in body length), with the larger species reaching in length, including legs. In practice, the respective
Arthropod swimming appendages and to filter food particles out of water; aquatic insects, which are air-breathers, use thick felt-like coats of setae to trap air, extending the time they can spend under water; heavy, rigid setae serve as defensive spines. Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, some still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors; for example, all spiders extend their legs hydraulically and can generate pressures up to eight times their resting level. The exoskeleton cannot stretch and thus restricts growth. Arthropods therefore replace