AEACHNIDA. 



155 



surface of the abdomen by as many distinct apertures or spiracles 

 (fig. 101, C). 



The Scorpions live in the warmer regions of the temperate zone 

 and in tropical countries, and are 

 generally found hiding under 

 stones or iu the crevices of walls. 

 They live upon insects, which 

 they catch with the great nipping- 

 claws, and sting to death with the 

 telson. 



Related to the true Scorpions, 

 though belonging to a special 

 group, are the little " Pseudo- 

 scorpions " or " Book-scorpions " 

 (fig. 103, A). These are small 

 Arachnidans, which are common- 

 ly found among old books, and 

 which look very like Scorpions in 

 miniature, this being due to the 

 fact that the maxillary palpi are 

 of great size and terminate in 

 pincers. Related to these, again, 

 are the " Harvest-men " {Pkal- 

 angium, fig. 103, B), which are 

 distinguished by the great length "'^ ^"i*--^' Book-scorpion (CMi/er), 

 *=> •! o to magnified ; B, PJialangium copiicum, 



and slenderness of their legs. of the natural sLse. 



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 by other characters. In all the true Spiders 

 (fig. 104) the segments 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 

 eifected by means of pulmonary sacs, conjoined with tracheee. The 

 pulmonary sacs are two or four in number, and open on the under 

 surface of the abdomen by as many apertures. The head bears 

 from two to eight simple eyes ; the mandibles (fig. 104, B) are 

 hooked, and caiTy the duct of a poison-gland ; and the maxillary 

 palpi are not developed into nipping-claws. The Spiders are all 

 predacious and rapacious animals, and many of them possess the 

 power of constructing webs, either for the capture of their prey, or 



