CHAPTER XIII 



ARACHNIDA EMBOLOBRANCHIATA (CONTINUED) ARANEAE 



EXTERNAL STRUCTURE INTERNAL STRUCTURE. 



Order III. Araneae. 



(ARANEIDA, 1 ARANEINA.) 



Arachnida breathing by tracheae and " lung-books." Cephalo- 

 thorax and pedicellate abdomen, the latter usually soft, and only 

 very rarely showing any traces of segmentation. Two-jointed non- 

 chelate chelicerae, the distal joint bearing the orifice of a poison- 

 gland. The tarsal joint of the male pedipalp develops a sexual 

 organ. The abdomen is furnished with spinning mammillae. 



THE true Spiders can readily be distinguished from allied Arachnid 

 groups, with which they are often popularly confounded, by the 

 presence of a narrow constriction or " waist " between the 

 cephalothorax and abdomen, and of a group of " spinnerets " or 

 external spinning organs beneath the hind portion of the body, 

 Thus the so-called " Harvest-spider " or " Harvestman " is clearly 

 not a Spider, for there is no constriction of its body into two 

 parts, nor does it possess any spinnerets. It belongs to the 

 Phalangidea. The same considerations will exclude the " Red 

 Spider " of popular nomenclature, which must be referred to the 

 Acarina or Mites. 



The Araneae, even as at present known, form a very extensive 

 and widely-distributed order of animals. Compared with certain 

 insect orders, they have received little attention from the collector, 



' J The term mostly in use is Araneida, which should mean Araneus-like animals. 

 This is clearly not allowable, unless there is a genus Araneus or Aranea. For 

 many years there has been no such genus recognised, but Simon now attempts to 

 re-establish it, inadmissibly, as it appears to us. (See note, p. 408). 



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