648 



ZOOLOGY 



SECT. 



FIG. 553. Spider (Epeira diadema). 



The Pedipalpi, or Scorpion-spiders (Fig. 551), are intermediate in 

 some of their external features between the Scorpions and the 

 Spiders. The abdomen is broad and marked out into a series 



of eleven or twelve distinct seg- 

 ments ; in one of the genera of the 

 order there is a short post-abdomen 

 formed of the last three segments, 

 with an elongated, many- jointed 

 anal filament. The chelicerae end in 

 simple claws ; they are probably 

 provided with poison-glands ; the 

 pedipalps are very long, either claw- 

 like or chelate ; the first pair of legs 

 are very long and slender, their 

 terminal part made up like an- 

 tennae of numerous short joints. 

 There are eight eyes on the cara- 

 pace, two larger central, and six smaller marginal. 



The Solpugida (Fig. 552) have, at least superficially, the appearance 

 of being intermediate between the Insecta and the other groups 

 of Arachnida. 

 The cephalo- 

 thoracic region 

 is divided by a 

 constriction 

 into two parts, 

 head and 

 thorax, the 

 latter made up 

 of three seg- 

 rn e n t s . The 



chelicerse are chelate ; the pedipalpi resemble the legs, and are used 

 in locomotion. The first pair of legs are attached to the head. 

 The abdomen is distinctly segmented, and there is no caudal 



appendage. A pair of poison-glands 

 open at the bases of the chelicerae. There 

 are two simple eyes on the head. 



In the true Spiders (Fig. 553) the 

 abdomen is rounded, unsegmented, and 

 separated off from the cephalothorax by 

 a constriction. The chelicerae (Fig. 554, A) 

 are sub-chelate, and the duct of a large 

 FIG. 555. Pedipaip of male of poison-gland opens at the extremity. 



Epeira diadema. //. ///. j- i /-ry en n\ ^ 



iv. v. podomeres : bb, sac ; sph. Ihe pedipalpi (.rig. 554, B) are elon- 

 gated, six-jointed, and end in simple 



extremities ; in the male (Fig. 555) the terminal joint is modi- 

 fied to serve for the reception and transference of the sperms. 



FIG. 554. A, Chelicerse, and B, pedipalpi of female of Epeira 

 diadema. (After Leuckart.) 



bh 



