THE HOG LOUSE, HAEMATOPINUS SUIS LINNE: 
ITS BIOLOGY, ANATOMY, AND HISTOLOGY! 
LAURA FLORENCE 
Because of their habitat on man and beast, lice have been known from 
the earliest times. Their systematic position has been a subject of 
controversy for more than a century, and the hog louse, on account of 
its large size and wide distribution, has frequently been used for the study 
of the morphology of the order. About the middle of the nineteenth 
century there was a controversy among physicians and entomologists as 
to the nature of the mouth parts of the pediculi infesting man, and the 
mouth parts of the hog louse were brought into the discussion by Bur- 
meister. A detailed account of this discussion is given in a paper by 
Schjédte (1864, English trans. 1866:213). Since the pediculi infesting man 
have been shown to be an etiological factor in the transmission of certain 
diseases, much accurate work has been done on their life history and 
morphology, and the many points of interest raised through such detailed 
study suggested that a parallel study of an animal parasite might be 
equally profitable. The aim of the present work has been to give an 
accurate account of the general internal anatomy of the hog louse, with 
a detailed description of the histology of certain parts. The relation 
between the parasite and its host has not been considered, and references 
to veterinary literature do not appear in the bibliography. 
The study was begun in 1917 in the Entomological Laboratory of 
Cornell University under Dr. William A. Riley, now of the University of 
Minnesota, and was continued under Dr. O. A. Johannsen, to both of 
whom thanks are due for helpful criticism. Since June, 1918, by the 
courtesy of the ‘Scientific Directors of the Rockefeller Institute, and, in 
particular, of Dr. Theobald Smith, Director of the Department of Animal 
Pathology, it has been made possible for the writer to complete the 
investigation. 
1From the Department of Entomology of the New York State College of Agriculture at Cornell Uni- 
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partial fulfillment of the requirements for the degree of doctor of philosophy. 
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