24 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 
sometimes under the apex. This genital plate or lamina corresponds to 
the apical part of the female digital, but the digital claw is entirely 
wanting, or rudimentary and hidden by pubescence. The genital organ is 
placed under the base of the lamina, It is furnished with processes vary- 
ing in form, size, and number, and with a hook or tube (or tubes) which 
fit into corresponding cavities in the female organ, and transfer the semi- 
nal fluid thereto. This peculiar formation does not appear until the last 
moult, when the spider is mature. Previous to that the male digital is 
simply a hairy bulb. The term genital bulb is also applied to the genital 
organ. Sometimes the bulb is quite one with the lam- 
ina in which it is muffled, in which case the bulb is 
ralled the claya,? 
During the interval between the third and fourth 
moulting a considerable change takes place. In the 
male the extremities of the palpi swell like clubs and 
develop into different indentations, teeth, threads, or 
leaves, which later on serve as transmitters of 
the semen, At first the clubs are filled with 
semitransparent fluid, while the forming inner 
organs are yellowish or brownish; at first the skin is 
quite soft, but soon hardens and forms a shell, which 
turns darker by the action of the air. Inasmuch as 
these organs are almost devoid of soft parts it follows 
--el 
Moulting 
Changes. 
Edie 
Fic. 13. Leg of Epeira 
magnified. Cx, coxa, 
the joint which unites 
the leg with the ster- 
num; tch, trochanter, 
small joint by which 
the femur articulates 
upon the coxa; fm, fe- 
mur; ptl, patella; tb, 
tibia; mt, metatarsus; 
t, tarsus; cl, claws. 
tacles for the semen, and is what is designated as 
naturally that as the shell cannot come off, no further 
moulting can take place. 
At the time the palpi become fully developed a 
great change takes place also in the female genitals ; 
the immediate surroundings become roughened and 
somewhat hardened, presenting little humps which serve 
partly as rests for the male palpi and partly as recep- 
“vulva.”? When fully 
matured the sexes, hitherto separated, come together, and the copulation 
takes place in a different manner by different varieties. * 
The legs of the spider are eight, symmetrically disposed, four on each 
side of the sternum to which they are articulated. 
give one of the best characters for systematic arrangement, They 
are numbered from the face backward as first (1), second (2), 
third (3), and fourth (4) pairs. 
The 
Legs. 
Their relative lengths 
(Fig. 11.) The relative lengths 
are indicated by a formula composed of the above numerals arranged in 
the order of greatest lengths from highest to lowest, thus: 1 2 4 3 is the 
formula which expresses the prevailing order among Orbweavers and de- 
! Westring, Araneze Sveciw, page 12. 
* Menge, “ Die Preussische Spinnen.” 
§ See Chapter on “Wooing and Mating Habits,” Vol. I. 
