CEA PIE Ri Xr 
ARACHNIDA (CON TINUED )—EMBOLOBRAN CHIATA—SCORPIONIDEA— 
PEDIPALPI 
SUB-CLASS IIl—EMBOLOBRANCHIATA(’ 
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 sia-jointed mesosoma and a 
sia-jointed tail-like metasoma, ending in a poison-sting. There 
are four pairs of lung-books, and the second mesosomatic segment 
hears 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. 
1 Cf p. 258. 
297 
