BY

CECIL WARBURTON, M.A.

Christ’s College, Cambridge; Zoologist to the Royal Agricultural Society

CHAPTER XII
ARACHNIDA (CONTINUED)—EMBOLOBRANCHIATA—SCORPIONIDEA—PEDIPALPI

SUB-CLASS II.—EMBOLOBRANCHIATA.[[238]]

Order I. Scorpionidea.

Segmented Arachnids with chelate chelicerae and pedipalpi. The abdomen, which is broadly attached to the cephalothorax or prosoma, is divided into two regions, a six-jointed mesosoma and a six-jointed tail-like metasoma, ending in a poison-sting. There are four pairs of lung-books, and the second mesosomatic segment bears a pair of comb-like organs, the pectines.

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.