A scorpion is a predatory arachnid of the order Scorpiones. They have eight legs and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always ending with a stinger. Scorpions have been around for hundreds of millions of years and are nothing if not survivors. They mainly live in deserts but have adapted to a wide range of environmental conditions and can be found on all continents except Antarctica. There are over 2,500 described species, with 22 extant (living) families recognized to date. Scorpions primarily prey on insects and other invertebrates, but some species hunt vertebrates. They use their pincers to restrain and kill prey, or to prevent their own predation. The venomous sting is used for offense and defense. During courtship, the male and female grasp each others pincers and dance while he tries to move her onto his sperm packet. All known species give live birth and the female cares for the young as their exoskeletons harden, transporting them on her back.