Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger. Scorpions range in size from 9 mm (Typhlochactas mitchelli) to 21 cm (Hadogenes troglodytes).Scorpions are found widely distributed over all continents, except Antarctica, in a variety of terrestrial habitats except the high latitude tundra. Scorpions number about 1,752 described species, with 13 extant families recognised to date. The taxonomy has undergone changes and is likely to change further, as a number of genetic studies are bringing forth new information.
Though the scorpion has a fearsome reputation as venomous, only about 25 species have venom capable of killing a human being.
The word scorpion is thought to have originated in Middle English between 1175 and 1225 AD from Old French skorpiō, or from Italian scorpione, both derived from the Latin word scorpio, which in turn has its roots in the Greek word σκορπίος – skorpíos.
Scorpions are found on all major land masses except Antarctica. Scorpions did not occur naturally in Great Britain, New Zealand and some of the islands in Oceania, but have now been accidentally introduced in some of these places by human trade and commerce. The greatest diversity of scorpions in the Northern Hemisphere is to be found in the subtropical areas lying between latitudes 23° N and 38° N. Above these latitudes, the diversity decreases, with the northernmost occurrence of scorpions being the northern scorpion Paruroctonus boreus at 50° N.
Today, scorpions are found in virtually every terrestrial habitat, including high elevation mountain-tops, caves and intertidal zones, with the exception of boreal ecosystems such as the tundra, high-altitude taiga and the permanently snow-clad tops of some mountains. As regards microhabitats, scorpions may be ground-dwelling, tree-living, lithophilic (rock-loving) or psammophilic (sand-loving); some species such as Vaejovis janssi are versatile and found in every type of habitat in Baja California while others occupy specialised niches such as Euscorpius carpathicus which occupies the littoral zone of the shore.
