Scorpiones (scorpions; subphylum Chelicerata, class Arachnida) Order of what are considered to be the most primitive arachnids, which have retained the division and segmentation of the abdomen. Scorpions have changed little since the Silurian. The prosoma is covered by a carapace and broadly joins the segmented abdomen, which is divided into a wide, anterior mesosoma (pre-abdomen), and a long, posterior metasoma (post-abdomen). The latter consists of a series of ring-shaped segments terminating in a telson in the form of a sting with associated poison glands. The chelicerae are very small, and the pedipalps are armed with large pincers. Scorpions are usually yellow to brown or black, more rarely greenish or bluish, and all fluoresce in ultraviolet light. All except cavernicolous species have a pair of median eyes and two-five pairs of lateral eyes on the carapace margin. Sensory organs include slit organs, sensory setae, and trichobothria, as well as pectines responding to touch and vibration frequencies above 100 Hz. Most scorpions sting in defence or to subdue struggling prey, and although the poison may be strong and even effective against vertebrates, they themselves are immune. Members of the family Buthidae are dangerous to humans, the poisons being neurotoxic in action. Mating involves the deposition of a spermatophore by the male, and an often lengthy and complex courtship ending with the female being led and pulled over the spermatophore, whereupon she takes the apical portion into her gonopore. Members of the Scorpionidae are viviparous, and as in all arachnids there is a high degree of parental care. Most of the 700 or so known species, distributed among six families, are tropical and subtropical, but the European species Euscorpius germanus is found in the southern Alps, and E. flavicaudis has been found in Kent, England. The largest known species is the African Pandinus imperator, which reaches 170 mm in length.

scorpions See ARACHNIDA; SCORPIONES.

scorpions See CHELICERATA.

scorpions See Arachnida.