Studies on Pedicutus 
204 
giving an account of the copulatory apparatus and the curious process 
of copulation in Pediculus humanus Linn4 
It is remarkable, in view of the mass of hterature that has been 
published on lice, dating from the time of Leeuwenhoek, that the 
subject of this paper has remained practically untouched. Where it 
has been approached, it has received scant treatment, and, as we shall 
see, the structure of the copulatory organs and mechanism of copulation 
have been misunderstood. This has doubtless been due to but a few 
casual observations having been made upon the living insects. 
We may begin by considering the main differences shown by the 
sexes in P. humanus, for some of them have a direct bearing upon the 
subject in hand. These differences concern chiefly the general body 
form, pigmentation, the structure of the legs, what may be visible of 
the genitalia viewed externally, the distribution of the hairs upon the 
abdomen, and the abdominal musculature. A number of these points 
of difference have been dwelt upon by previous authors and they are 
summarized as follows: 
CERTAIN ESSENTIAL DIFFERENCES IN THE ANATOMY 
OF THE SEXES. 
{Exclusive of the generative organs.) 
The Male. The abdomen of the male is rounded behind, the ventral 
surface curving dorsally and forward so that the sexual and rectal 
orifices come to lie dorsally (Text-fig. 3). The anus lies just in front of 
the sexual orifice; its position is best indicated when the insect defaecates 
whilst feeding or immediately afterwards. The anus is marked by a 
minute pit with a small ventrally situated chitinous plate overlapped by 
a dorsal integumentary fold. Immediately behind the anal plate lies 
the broad transverse slit forming the sexual aperture from which the 
'I'o avoid confusion 1 append the following Synonymy: 
Prd inti II ■‘t hiitnanii.s Linn. 17.')S. 
P. capitis do Geer 1778 | 
P. ccnncalis [.atreille ISO.*? r lice from head. 
P. roiisohrini's Piaget 1880 ) 
P. rorparis do Geer 1778 j 
P. vestimenti Nitzscli 1818 lice from clothes and body. 
P. tahcsceiititiin Alt 1824 ) 
Most authors recognize what they hold to be two .species the head lou.se and clothes or 
body louse. These are, however, identical in all points of structure and can no longer be 
regarded a.s distinct, though they may. show slight biological ditference.s. The studie.s 
here reeordi'd have Ix'en cani('d out on so-ealled “ P. rrstimciili." 
