nscorpionidaAn order of Arachnida, having pulmotracheate respiration, the cephalothorax indistinctly segmented from the abdomen, a long jointed postabdomen ending in a hook or telson, and long maxillary palpi, or pedipalps, ending in a usually large chelate claw, or pincer; the true scorpions or Scorpiones. The ambulatory legs are seven-jointed, and of moderate and approximately equal lengths. The eyes are from six to twelve in number. The falces or cheliceræ are well developed and pincer-like. There are four pairs of pulmotracheæ. The long postabdomen or tail is very flexible, and is generally carried curled up over the back; the hook with which it ends is perforated for a poison-duct, and constitutes a sting, sometimes of very formidable character. The order is very homogeneous, and all the forms of it were formerly included in a single family, Scorpionidæ, or even in the genus Scorpio. It has been divided, according to the number of eyes (six, eight, ten, or twelve), into Scorpionidæ, Telegonidæ, Vejovidæ, and Androctonidæ, and in other ways. From 1 to more than 30 genera are recognized. See cut for Scorpionidæ above, and those under Buthus and scorpion.
Chambers's Twentieth Century Dictionary
Scorpionidaan order of Arachnida, containing the Scorpiones or true scorpions