The External Anatomy of Spiders 



The Aranea Type of Palpus. — I have selected the palpus of Aranea 

 frondosa as an example of an extremely specialized palpus. In Fig. 104 

 the entire palpus, with the bulb unexpanded, is represented slightly twisted 

 so as to show the ventral aspect of the proximal segments and the lateral aspect 

 of the bulb. 



The proximal segments of the palpus. — This account of the palpi of male 

 spiders is devoted almost entirely to a discussion of the parts of the tarsus, the 

 proximal segments being well understood; there are, however, a few features of 

 these segments in the aranea type that merit attention here. 



Upon the coxa there is a prominent spur, the coxal spur (Fig. 104, c. s.)\ and 

 upon the inner side of the femur near its base, there is a groove, the femoral groove, 

 into which the coxal spur fits when the palpus is extended forward. The presence 

 or absence of this spur and groove is an 

 important generic characteristic in the 

 Araneinaj. 



The patella bears two prominent 

 spines at its apex (Fig. 104, p.). This is 

 also true in the males of several other 



Fig. ios. LATERAL ASPECT OF AN 



EXPANDED BULB OF ARANEA 



FRONDOSA 



Fig. 106. MESAL ASPECT OF AN 

 EXPANDED BULB OF ARA- 

 NEA FRONDOSA 



genera; but in the greater number of genera of the Araneinae there is only a single 

 spine in this position. 



The most striking feature of the tibia is its shortness, it being of about the 

 same length as the patella. 



The tarsus.- — As in Linyphia. the tarsus of Aranea consists of two parts: 

 the cymbium and the paracymbium. Hut in Aranea the paracymbium (Fig. 

 105, p. c.) is merely a prominent apophysis arising from the base of the cymbium 

 and is not articulated with the cymbium by a movable joint as in Linyphia and in 

 Pachygnatha. The alveolus is much more extended than it is in Linyphia; here it 

 occupies nearly the whole length of the cymbium (Fig. 105, a). 



The unexpanded bulb. — In the unexpanded bulb of Aranea frondosa, the 

 subtegulum (Fig. 104, s. teg.), tegulum (Fig. 104, teg.), and a terminal lobe of the 

 apical division of the bulb, bearing a long and slender terminal apophysis (Fig. 



114 



