ARACHNIDA. 153 
scorpions the end of the abdomen (fig. 73) is composed of a 
hooked telson, which is perforated for the duct of a poison- 
gland, situated at its base. It is by means of this that the 
scorpions sting ; and the poisonous fluid which they secrete is 
sufficiently powerful to render their wounds troublesome and 
painful, if not positively dangerous. The mandibles in the 
scorpions, as already said, are developed into pincers, and the 
so-called ‘‘maxillary palpi” constitute powerful nipping-claws. 
The respiratory organs are in the form of pulmonary sacs, four 
on éach side, opening on the under surface of the abdomen by 
as many distinct apertures or spiracles (fig. 71, 3). 
The scorpions live in the warmer regions of the temperate 
zone and in tropical countries, and are generally found hiding 
under stones or in the crevices of walls. Their sting, though 
much exaggerated, is certainly capable of producing very un- 
pleasant symptoms.” 
ORDER IV. ARANEIDA.—In this order are the true Spiders, 
readily distinguished from the insects, with which they are 
popularly confounded, by having four pairs of legs, as well as 
Fig. 74.—Araneida. Zheridion riparium (female). 
by other characters. In all the true spiders (fig. 74) the seg- 
ments of the thorax and head are united to form a single mass 
or cephalothorax, to which the soft and unsegmented abdomen 
is joined by a constricted stalk or neck. Respiration is effected 
by means of pulmonary sacs, usually conjoined with trachee. 
* Nearly allied to the Scorpions are the so-called ‘‘ Harvest-spiders” (Phalan- 
gide), and the diminutive ‘‘ Book-scorpion” (Chelifer), which is commonly to be 
found amongst old books. 
