Order Araneida 



includes a single family, the Liphistiidae, represented by a single 

 known genus, Liphistius, which is doubtless the most generalized 

 of the living members of the order Araneida. 



The most strik- 

 ing characteristic of 

 this genus is the fact 

 that the abdomen, 

 when seen from above, 

 appears to be distinct- 

 ly segmented; there 



Fig. 210. PROFILE OF LIPHISTIUS (after Warburton) being a Series of Well- 



marked tergal plates 

 (Fig. 210). The ventral surface of the first and second segments 

 are furnished also with sternal plates, covering the genital aperture 

 and the two pairs of book-lungs. 



The two pairs of abdominal legs that are preserved as spin- 

 nerets are each two-branched, thus forming eight spinnerets. 

 These are situated near the middle of the ventral aspect of the 

 abdomen (Fig. 210). It was this fact that suggested the name of 

 the suborder, Mesothelae being from meso, middle and thele, teat. 



The only known species are found in Sumatra. 



Suborder OPISTHOTHELiE (O-pis-tho-the'lae) 



In this suborder, which includes all American spiders, the 

 abdomen is not segmented. And the spinnerets are situat- 

 ed near the posterior end of the abdomen close to the anus. 

 The name of the suborder is from opisthen, behind and thele, 

 teat. 



In this suborder we find only six spinnerets, the first pair 

 being unbranched. It has been suggested that the inner branches 

 of the first pair are represented in some spiders by the cribellum, 

 and in others by the colulus. 



This suborder includes more than forty families; representa- 

 tives of thirty of these have been found in America north of 

 Mexico and are discussed in the following pages. 



The families of this suborder represent two quite distinct 

 groups of families, each of which may be considered a super- 

 family, and designated as the Avicularioidea and the Argiopoidea 

 respectively. The Avicularioidea includes the tarantulas, char- 



220 



