22 



AMERICAN SPIDERS AND THEIR SPINNING WORK. 



Mandi- 

 bles. 



The part of the caput included between the two rows of eyes is called 

 the eye space. The space between the front row of eyes and the lower 

 margin of the face where it joins upon the mandibles is the clypeus 



(Cp). That between the upper row of eyes and 

 the vertex (v) of the caput is the forehead. The 

 entire space thus occupied, from the vertex to the 

 margin of the clypeus, is the face or facial space. 

 The mandibles (nib) are two jaw like organs 

 attached to the head beneath the margin of the 

 clypeus, within which they articulate lat-' 

 erally. They are placed perpendicularly, 

 or inclined more or less backward or 

 toward the sternum. In shape they are conical or 

 subovate. Each mandible is composed of two parts, 

 the base or falx (fx) and the fang (fg). The fang 

 is a curved movable tooth, smooth, hard, and 

 aa--' ■"" -^'^ pointed. It is hollow, pierced on the inner side 



Fig. 10. Ventral view of Argiope near the poiiit with a Small hole, which opens into 



argyraspis. ps, palps; mb, t i , p mi 



mandible ; dg, digital joint of a Slight turrOW. i he 



palps; ra, radial joint; hu, holloW of the fang is 

 humeral ; cu, cubital ; ax, ax- . " 



illary; mx, maxillae; lb, labi- OCCUpicd by a mcmbra- 



um;sm, sternum; ex, coxa of ^-^^^g ^^^^ ^j^-^j^ j^.^j 

 the leg; gl, breathing gills; ep, 



epyginum ; sp, spinnerets rep- Upward tO a gland 



resented closed; ac, anal clos- in i -j.! • xi r i 



ure. lodged Within the falx. 



This gland is supposed 

 to secrete a poisonous liquid. 



The falx is covered with hair, especially 

 near the base, and at the apex is formed 

 into a toothed groove or sheath 

 into which the fang is folded down 

 when at rest. 



The sternum (sm) is a cordate plate which 

 forms the under part of the shell of the 



cephalotliorax. It has four iiiden- 

 Sternum. ... ^ ■ -, i . , 



Labium. ^''^^^'^'^ ^^^ ^^^^^ side, which mark 



the insertion of legs. On the for- 

 ward i)art at the middle is placed the labium 

 or lower lip (lb), a subtriangular or semi-ovate 

 organ of the mouth. (See Fig. 10.) 



0[)posed to tlie labium and above it is 



Falx. 



Fig. 11. Dorsal view of Epeira insularis. 

 ab, abdomen ; b, base ; ap, apex of ab- 

 domen ; pt, pits which mark the attach- 

 ment of abdominal muscles ; cp, ceph- 

 alic part of cephalotliorax ; tp, thoracic 

 part; mb, mandibles. 1, 2, 3, and 4, 

 the legs represented in their order, 

 first, second, third, and fourth. Teh, 

 trochanter of the leg; ex, coxa; fm, 

 femur ; dg, digital, ra, radial, cu, cu- 

 bital, hu, humeral joint of palps. 



the ui)[H"r lip, a slight hair tipped projection, 



Maxillce. ^^'''^^^' '^^ ^^^^ termination of the i)alate. On either side of the 



l.ihiiirn is placed one of the maxilhe or lower jaws. They vary 



III form, tlit^ variation giving good generic characters. They have a 



