Upon viewing some of the larger spiders (e.g. tarantulas, wolf spiders), many people are surprised to find that they appear to have ten legs, rather than eight. That's because apart from their legs, they also have two arm-like limbs calld pedipalps. These are used for seizing their prey, and in the case of males, they also use them for mating purposes. They dip the pedipalp tips in their own sperm webs, this infusing them with live sperm cells.