SCORPION

(order Scorpionida), any of the 1,200 to 1,300 species of arachnids characterized by an elongated body and a segmented tail that is tipped with a venomous stinger. Scorpions range in size from 13 to 175 mm (0.5 to 7 inches) and have six pairs of appendages. The chelicerae, the small first pair, are used to tear apart prey. The pedipalps, the second pair, are large and have strong, clawlike pincers, which are held horizontally in front and are used as feelers and for grasping prey. The last four pairs, each equipped with a pincer, are walking legs. Scorpions are nocturnal and feed mainly on insects and spiders. They grasp the prey with their large, powerful pedipalps and tear it apart, sucking the tissue fluids. Large prey is usually paralyzed with the venom injected by the stinger before it is eaten. During mating the male and female perform a courtship dance. The purpose of this behaviour is twofold: the male must find level ground on which to deposit the sperm-containing spermatophore, and he must position the female over the spermatophore so that she may accept it. After the spermatophore is accepted, the male is often devoured by the female. Fertilized eggs develop inside the female, and the young, which are born alive, stay on the female's back for about 12 days. At least two general types of scorpion poison exist. One is a hemotoxin that causes mild to severe local effects such as edema, discoloration, and pain; the other is a dangerous neurotoxin (nerve poison) that may cause severe local and systemic effects such as convulsions, paralysis, cardiac irregularities, and death. Most scorpions prefer to retreat rather than to fight and do not sting humans unless provoked. any member of the order Scorpiones, or Scorpionida, of the class Arachnida. The animals have an elongated body and a segmented, curved tail tipped with a venomous stinger. Grasping, fingerlike first appendages are other typical features. Scorpions often play the role of evildoers in fables and legends; Greek respect for scorpions prompted the naming of the constellation Scorpio, a sign of the zodiac. Additional reading The scorpions are treated in J.L. Cloudsley-Thompson, Spiders, Scorpions, Centipedes, and Mites, new ed. (1968), a general account of natural history and ecology; and Erik N. Kjellesvig-Waering, A Restudy of the Fossil Scorpionida of the World (1986), the best work on fossil scorpions, with comments on the modern fauna. Gary A. Polis The Editors of the Encyclopdia Britannica