The Scorpions include the largest tracheate Arachnid forms, and show in some respects a high grade of organisation. It is impossible, however, to arrange the Arachnida satisfactorily in an ascending series, for certain primitive characteristics are often most marked in those Orders which on other grounds would seem entitled to rank at the head of the group. Such a primitive characteristic is the very complete segmentation exhibited by the Scorpions. They are nocturnal animals of rapacious habit. In size they range from scarcely more than half an inch to eight inches in length. In the northern hemisphere they are not found above the fortieth parallel of latitude in the Old World, though in the New World they extend as high as the forty-fifth. A corresponding southward limit would practically include all the land in the southern hemisphere, and here the Order is universally represented except in New Zealand, South Patagonia, and the Antarctic islands. Fossil scorpions are rarely found. The earliest examples known occur in the Silurian rocks, and belong to the genus _Palaeophonus_. In the Carboniferous _Eoscorpius_ is found, and in the Oligocene _Tityus_. Much remains to be discovered with regard to the habits of scorpions, and most of the isolated observations which have been recorded lose much of their value through the uncertainty as to the species concerned. The brief accounts given by Lankester and by Pocock,[239] and the more recent and elaborate studies of Fabre,[240] are free from this defect and contain almost the only trustworthy information we possess. All are viviparous, and the females carry the newly-hatched young on their backs. They are predaceous, feeding for the most part on insects and spiders. These are seized by the chelate pedipalps, and, if small, are simply picked to pieces by the chelicerae and devoured, but if large the tail-sting is brought into play and the victim quickly paralysed. The process of eating is a slow one, and a Cape scorpion in captivity took two hours to devour a cockroach.