Scorpions are a group of predatory arachnids including over 1,700 species. Their most distinctive features are their large front pinchers and an arched tail with a venomous stinger. Scorpions are found in a wide variety of habitats, from the tundra to deserts, and are generally nocturnal. They also vary widely in size, from half an inch long to almost a foot in length. All scorpions are capable of giving a painful sting, but only 25 species are potentially fatal to humans.