The Hog Louse 653 



transverse split; the chitin on each side of the median rupture is stretched 

 back so that the opening resembles a triangle. The first pair of legs is 

 next withdrawn, and these, pushing down the skin, help in the final freeing 

 of the head and the mouth parts. These now occupy their normal position, 

 and the second and then the third pair of legs are withdrawn, pushing the 

 insect forward and freeing it from the old skin, which remains anchored 

 to the surface upon which the insect has emerged. The process took 

 place when a louse had been put on the arm to feed and was watched 

 through a binocular. From the first rupture of the old skin until the 

 complete emergence of the insect, thirty minutes elapsed; Sikora (1915: 

 525-526) describes the process in Pedicidus vestimcnti as lasting but five 

 minutes. No description of the act has been found in the literature of 

 the hog louse, and the slowness in the case observed may have been due 

 to the unnatural environment of the insect; moreover, death followed 

 within an hour of molting. 



THE ADULT LICE 



The male and the female are recognized by their dilTerence in size, the 

 shape of the abdomen, and the structure of the two posterior abdominal 

 segments. Both are without pigmented ej^es, but the projections on the 

 sides of the head have a lateral, slightly convex, refractive surface sugges- 

 tive of a lens. While the thorax of the female is somewhat shorter and 

 broader than that of the male, the legs of the sexes are identical, showing 

 no modifications for clasping in relation to copulation. No constant 

 variations in pigmentation have been observed. 



THE MALE 



The abdomen of the male is considerably shorter than that of the female, 

 so that, although it measures the same or even slightly less in its widest 

 region, it appears considerably broader. The tergites of segments 1 and 

 2 are small, but clearly defined. Hairs are present in each abdominal 

 segment in a transverse row. Posteriorly the abdomen is rounded; the 

 terminal segment curves dorsad and anterior, bringing the rectal and 

 sexual orifices into a dorsal position (Plate LVHI, 8). On the ventral 

 surface there is a strongly chitinized plate of characteristic shape extending 

 from the transverse median line of segment 7 through segment 8 to seg- 

 ment 9, its posterior edge being visible from the dorsal aspect of the 



