22 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



7ITX 

 sm. 



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 (mb) are two jaw like organs 

 attached to the head beneath the margin of the 

 clypeus, wdthin 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 

 pointed. It is hollow, pierced on the inner side 

 FIG. 10. ventral view of Argiope near the point w r ith a small hole, which opens into 



argyraspis. ps, palps; mb, ,. , ^-i 

 mandible ;dg, digital joint of a slight furrOW. I he 

 palps; ra, radial joint; hu, hollow of the fang IS 

 humeral; cu, cubital; ax, ax- 

 illary; mx, maxiiia; ib, labi- occupied by a mem bra- 

 um ; sm, sternum; ex, coxa of noug duct which leadg 

 the leg; gl, breathing gills ; ep, 



epyginum ; sp, spinnerets rep- Upward to a gland 



resented closed ;ac, anal clos- foft^ 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 P 

 when at rest. 



The sternum (sm) is a cordate plate which 

 forms the under part of the shell of the 



aa- 



cu 



P~ 



..-dg 



CCphalothoraX. It has four inden- FIG. n. Dorsal view of Epeira insularis. 

 tations On each Side, Which mark ab, abdomen ; b, base ; ap apex of ab- 



domen ; pt, pits which mark the attach- 

 the insertion Of legS. On the for- ment of abdominal muscles ; cp, ceph- 



Sternum. 

 Labium. 



ward part at the middle is placed the labium 



Or lower lip (Ib), a Subtrianglllar Or Semi-OVate the legs represented in their order, 



P ,1 /a -m- tf\\ first, second, third, and fourth. Teh, 



organ Ot the mOUth. (bee *lg. 10.) trochanter of the leg; ex, coxa; fm, 



Opposed tO the labium and above it is femur ; dg, digital, ra, radial, cu, cu- 



, . i i , i , bital, hu, humeral joint of palps. 



the upper up, a slight hair tipped projection, 



which is the termination of the palate. On either side of the 

 labium is placed one of the maxillae or lower jaws. They vary 



in form, the variation giving good generic characters. They have a 



