22 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 
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 (vy) 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, 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 
pointed. It is hollow, pierced on the inner side 
Fig. 10, Ventral view of Argiope near the point with a small hole, which opens into 
argyraspis. ps, palps; mb, 7 D r 
mandible; dg, digital joint of @ Slight furrow. The 
Mandi- 
bles. 
palps; ra, radial joint; hu, }ollow of the fang is Pp i ee dp 
humeral; cu, cubital; ax, ax- earner ee St a= Bele , 
ilary; mx, maxille; 1b, labic OCCUpied by a membra- cu Tag 
um; sm, sternum; cx, coxa of ae By FY nada =o Am. 
theleg; gl, breathing gills; ep, nous duct which leads ° nie oe OX 
epyginum ; sp, spinnerets rep- upward to a gland d----.! 
resented closed’; ae, ansi'cio® 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 P 
when at rest. 
The sternum (sm) is a cordate plate which 
forms the under part of the shell of the 
ee cephalothorax. It has four inden- fie. 11, Dorsal view of Epeira insularis. 
ernum. tations. om each side, whieh mark 7): stdomenib, bese) an) apse atets 
Labium. - 2 domen; pt, pits which mark the attach- 
the insertion of legs. On the for- ment of abdominal muscles; cp, ceph- 
: a en . alic part of cephalothorax; tp, thoracic 
ward part at the middle is placed the Jabium matt: ab, sasmdtblone f, cent 
or lower lip (lb), a subtriangular or semi-ovate the legs represented in their order, 
f f th th S Fj 10 first, second, third, and fourth. Tch, 
organ 0 16 Mouth, ( ee Pig. ») trochanter of the leg; cx, coxa; fm, 
Opposed to the labium and above it is ‘femur; dg, digital, ra, radial, cu, cu- 
* : - . 5 ; bital, hu, humeral joint of palps. 
the upper lip, a slight hair tipped projection, 
which is the termination of the palate. On either side of the 
labium is placed one of the maxilla or lower jaws. They vary 
in form, the variation giving good generic characters. They have a 
Falx. 
Maxille. 
