158 
Biology of Pediculus humanus 
is depressed whilst this is taking place. As in the process of hatching, 
described on p. 148, the louse, in the act of moulting, sucks up air into 
its pharynx, whence it passes into the gut, thus inflating the animal, 
and, passing backward, it escapes from the anus. At first the back of 
the thorax protrudes, then the first pair of legs, and these, pressing 
downward, help to free the head. As soon as the head issues it assumes 
its normal position and pumping ceases. The second and then the 
third leg-pair appear and help to remove the moult completely by 
Fig. 11. Pediculus humanus (corporis). Empty second larval skin from which a third 
stage larva issued. Note the convergence of the legs which hold the hair or cloth on 
which the insect emerges. Dorsally the old tracheae are seen protruding. The anterior 
portion of the head is bent sharply downward as one piece; the forked structure 
emerging dorsally, represents a portion of the complex of the piercing organ. The 
longitudinal split starts at the vertex and extends backward to the end of the thorax; 
the antennae and eyes are turned downward ventrally. 
pushing it backward. The first to observe the process was Sikora 
(vm. 1915, p. 525) and this author’s description is accurate if short; 
the process was seen to last 5 minutes, and 45 minutes later the louse, 
a 2nd stage larva, began to suck blood. The accompanying illustrations 
(Figs. 11, 12) show the appearance of the moult; Muller (1915, PI. I, 
Fig. 5) figures a moult accurately as it appears in profile. Certain 
matters in relation to moulting will receive attention in the section on 
anatomy. I would note, however, that the legs of the moult remain 
