320 
Studies on Pediculus 
its own size, a small portion of the basal portion of the sack and the 
whole of its stem remaining outside the greatly stretched vulva. As 
soon as the vesica is safely anchored by means of its teeth to the inside 
of the vagina, the male ceases to strain backward, the female’s abdomen 
again lengthens and the pair drop into a less acrobatic attitude upon 
their legs as shown in Text-fig. 11, and, united in copula, they retreat 
beneath a sheltering piece of cloth. 
This undoubtedly represents the usual procedure. On one occasion 
only was a male observed to seize the female by the bases of the second 
pair of legs. When on cloth and ready to copulate, the females are 
frequently seen to assume an attitude approximating to that shown in 
Text-fig. 10, the hind pair of legs and the abdomen being raised almost 
vertically as if inviting the male to approach and seize her. The pair 
remain united for a variable time, anywhere from half an hour to several 
hours. A male which has just ceased to copulate with a female has been 
seen to clamber on her back, seize her about the body with his six legs, 
she walking away with him. At other times the male has been seen to 
copulate again immediately after having abandoned a female. 
We may revert here to the differences already noted in the abdominal 
musculature of the sexes, since in part it bears directly upon the process 
of copulation. The more powerful dorsal system of longitudinal 
muscles in the male (compare Text-figs. 3 and 6) appears to be correlated 
with his ability to overcome the female in the effort to introduce his 
copulatory organs by arching his abdomen backwards and forcing the 
dilator forward ; doubtless these muscles also serve to keep his abdomen 
from being unduly pressed downward by the female’s weight during 
copula, especially when the pair move about. The latter suggestion as 
to the function of these muscles emanates from Muller who was the 
first to appreciate the differences in the musculature in the sexes. 
The legs as accessory organs of copulation. Previous authors have 
noted the form and greater size and especially the powerful claws of 
the first pair of legs in the male. It is clear that they are more powerful, 
so as to enable the male, as we have seen, to grasp the female firmly 
during copulation. There is, however, a corresponding adaptation in 
the structure of the third pair of legs in the female. But for two 
drawings of the female by Terzi (in Castellani and Chalmers, 1913, pp. 632 
-633, figs. 268, 270) the structure appears to have escaped the notice 
of previous observers; its significance has certainly not been under¬ 
stood hitherto. Although less pronounced in poorly chitinized females, 
the structure is invariably present. It consists (Text-fig. 12) of a blunt 
