126 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



d co- 



rn n- 



Pt-' 



to as "sterual cones," or simply "cones" (s.co). The labium (lab) and 

 maxillae (mx) are also shown in Fig. 92. 



VII. 



The parts of the abdomen referred to in description are as follows : 

 The dorsum (Fig. 93, do) is the rounded top of the back, of which the 

 anterior part is called the "base" (ba), and the posterior the 

 "apex" (ap). The "folium" (fol) is a leaf like figure which usually 

 occupies one-third or more of the middle part, extending longitudinally 

 from base to apex. The median line (mn) of the dorsum often has a 

 deeper shade of color than the edges of the folium. The blackish " pits," 

 or round dark spots (pt), symmetrically arranged in pairs on each side of 

 the median line of the folium, indicate points of attachment for internal 



muscles. The venter 

 (vn, Fig. 94) is the part 

 Ij^ng between the epi- 

 gynum (ep) and gills (gi) 

 and the spinnerets (sp) ; 

 pits or dimples may also 

 be. seen on the venter 

 symmetrically arranged 

 as on tlie dorsum. The 

 median ventral band is 

 ABDOMEN AND Parts. usually bordered by a 



Fifi. 93. Dorsal view; pd, pedicle uniting to cephalothorax ; ba, base or Strip of lighter Color 

 fore part; d.co, dorsal cones or shoulder humps; fol, folium or dorsal ,.,^f^,.p ^,, 1p«<s broken 

 pattern; ap, apex ; sp, spinnerets; pt, pit marking insertion of muscles: 



mn, median line of dorsum. Fii;. 94. Side view; vn. venter; ep, epi- When tllC abdomen is 

 gynum ; gi, breathing gills; other references as above. ii • i i j. xi 



^' '^ e B , thickened at the apex, 



the space between the dorsal and ventral ajiex is known as the apical 

 wall of the abdomen. On either side or shoulder of the dorsal base some 

 species have conical prominences known as dorsal cones or tubercles (d.co). 

 These are sometimes placed at several other points, usually along the mar- 

 gin of the dorsum. In some species these are hard and spinous. 



The exterior parts of the epigynum referred to in the descrijition are 

 illustrated at Figs. 95, 96. The atriolum vulvte, or vulval porch, is a 

 vaulted porch or hood that curves over the genital opening, in 

 front of which (anterior) it is located. It is usually ehitinous, 

 and covered at the base with hairs. The middle part in many 

 species is prolonged into a shaft or scapus atrioli, which is sometimes a 

 mere flap, and again is much lengthened. Sometimes it is smooth, some- 

 times wrinkled or rugose, often with a row of stout hairs thereon. Fre- 

 quently it is grooved or hollowed along the under surface. The tip is 

 more or less attenuated and rounded, or sometimes pointed ; in many 

 species it is widened into a bowl or spoon, usually oval, but sometimes 



Epigy 

 num. 



