120 
Biology of Pediculus humanus 
and, wandering off slowly to adjoining hairs, she came to rest. The 
whole act of oviposition, timed by a stop-watch, did not last over 
17 seconds, counting from the time the female began to slide back 
along the hair until she again moved forward abandoning the egg. 
The latter remained cemented upon the hair with the operculum 
v.pl 
Fig. 4. (A) Posterior ventral portion of ttie abdomen of Pediculus liumanus (corporis) $, 
illustrating the function of (gon.) the gonopods as claspers of human hair, whereby 
the insect is able to lay its eggs in alignment with the hair. At rest, the gonopods 
are directed backward or somewhat dorsally; when grasping a hair they are flexed 
downward as shown in Fig. 3. 'The hair passes backward between the (p. 1.) posterior 
lobes of the last abdominal segment- which are shaped for the purpose. Anterior 
to the gonopods lies the (v.pl.) ventral plate, the structures being pigmented and 
rigid, the pliable integument between them functioning like an interarticular mem¬ 
brane. The space between the gonopods and between the posterior lobes is adjusted 
to the calibre of human hair; they may, however, separate and have been seen to 
grasp two hairs. 
(B) An egg of Pediculus humanus (corporis) cemented upon a fine human hair 
and seen in profile; otherwise it is orientated in relation to the adjoining figure A, 
the pointed end being directed backward as the egg issues from the female; 
(D) the dorsal and (V) the ventral surfaces of the egg, (T) the cement tube sur¬ 
rounding the hair. 
Both figures drawn to. scale with the aid of a camera lucida. 
directed toward tbe female as she walked awav. Dr Keilin, who 
immediately afterwards confirmed my observation here described, was 
unable to time the act because it took place too rapidly. Whereas the 
female I observed was seen in profile, the female observed by Dr Keilin 
