THE HOG LOUSE, HAEMATOPINUS SUIS LINNfi: 

 ITS BIOLOGY, ANATOMY, AND HISTOLOGY i 



Laura Florence 



Because of their habitat on man and beast, hce have been known from 

 the earhest times. Their systematic position has been a subject of 

 controversy fbr 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 phjrgicians 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 

 Schjodte (1864, English trans. 18,66:213). 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 histologj^ 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. 0. 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. 



1 From the Department of Entomology of the New York State College of Agriculture at Cornell Uni- 

 versity, and the Department of Animal Pathology of the Rockefeller Institute for Medical Research. 

 Also presented to the Faculty of the Graduate School of Cornell University, June, 1920, as a thesis in 

 partial f ulfillm ent, of the requirements for the degree of doctor of ptiiiosophy. 



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