674 LAURA FLORENCE 
This suggestion was criticized by Enderlein (1904:121 and 1905:626), 
who. believed that these insects were hemipterous in their affinities, and 
consequently homologized the piercing apparatus with the maxillae, 
hypopharynx, and labium of the Rhynchota. His method of investi- 
gation was by gross dissection and by the study of cleared and mounted 
specimens. He used a number of related forms but gave the most detailed 
work to the interpretation of the hog louse. He compared the “mandi- 
bles” of the latter with those of the Corixidae, a proceeding which led 
to a discussion of the question by Handlirsch (1905:668), who emphasized 
the much clearer resemblance existing between the mandibles of the 
Siphunculata (Anoplura) and of different species of Mallophaga as figured 
by Snodgrass (1899). One outcome of the controversy between Cholod- 
kovsky and Enderlein was the publication by Pawlowsky (1906: 156) 
—a pupil of Cholodkovsky — of a résumé of the literature up to his 
time on the mouth parts of lice, 2nd a description of the anatomy of the 
piercing and sucking apparatus of the Pediculidae. 
Mjéberg (1910:203) made no study of the mouth parts but confined 
himself to a brief summary of the work of others, dealing at greatest 
length with Enderlein’s work on the hog louse and his interpretation 
of the mandibles. Patton and Cragg (1913:531) gave an account of 
the mouth parts of Pediculus vestimenti “‘ prepared, with the assistance 
of the above papers lof Enderlein and Pawlowsky], from sections and 
dissections.”” This account included also a description .of the first part 
of the alimentary canal. The fact that the man-infesting pediculi are 
an etiological factor in the transmission of certain diseases has led to the 
publication within the last few years of three detailed papers on the 
anatomical structure of the anterior part of the alimentary canal and 
of the mouth parts proper. Those of Harrison (1916b) and Sikora (1916) 
appeared almost simultaneously, and that of Peacock (1918) some two 
years later. Owing to war conditions the work of Sikora was not available 
to the other two investigators, nor their work to her. Harrison and 
Peacock confined their investigations to the species affecting man, while 
Sikora introduced several species, among them the hog louse, for purposes 
of comparative study. 
The head of the hog louse is most strongly chitinized on the lateral 
regions, and the chitinization extends a little way beyond the borders of 
both dorsal and ventral surfaces. The remainder of the ventral surface 
is only weakly chitinized, and at the anterior end the integument is 
