Scorpion

Scorpions are predatory arachnids of the order Scorpiones. They have eight legs[1] and are easily recognised by the pair of grasping pedipalps 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 / 0.3 in. (Typhlochactas mitchelli) to 23 cm / 9 in. (Heterometrus swammerdami).[2]

The evolutionary history of scorpions goes back to the Silurian era 430 million years ago. They have adapted to a wide range of environmental conditions and can now be found on all continents except Antarctica. Scorpions number about 1750 described species,[3] with 13 extant families recognised to date. Only about 25 of these species are known to have venom capable of killing a human being.[4]:1The taxonomy has undergone changes and is likely to change further, as genetic studies are bringing forth new information.

Scorpion stings are painful but are usually harmless. For stings from species found in the United States, no treatment is normally needed for healthy adults although medical care should be sought for children and for the elderly. Stings from species found elsewhere may require medical attention.




Etymology

The word scorpion is thought to have originated in Middle English between 1175 and 1225 AD from Old French scorpion,[6] or from Italian scorpione, both derived from the Latin word scorpius,[7] which is the romanization of the Greek word σκορπίος – skorpíos.[8]
Geographical distribution

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 now have been accidentally introduced in some of these places by human trade and commerce.[4]:249 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 natural occurrence of scorpions being the northern scorpion Paruroctonus boreus at Medicine Hat, Alberta, Canada 50° N.[4]:251

Today, scorpions are found in virtually every terrestrial habitat, including high-elevation mountains, 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.[4]:251–252[9] 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 specialized niches such as Euscorpius carpathicus, which occupies the littoral zone of the shore.[10]

Five colonies of scorpions (Euscorpius flavicaudis) have established themselves in Sheerness on the Isle of Sheppey in the United Kingdom.[11] This small population has been resident since the 1860s, having probably arrived with imported fruit from Africa. This scorpion species is small and completely harmless to humans. At just over 51° N, this marks the northernmost limit where scorpions live in the wild.