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A CONTRIBUTION TO THE KNOWLEDGE OF THE BOT-FLIES, 

 GASTROPHILUS INTESTINALIS, DeG., G. HAEMORRHOIDALIS, L., 

 AND G. NASALIS, L.* 



By S. Hadwen, D.V.S. 

 (Dominion Pathologist, Health of Animals Branch), 



and A. E. Cameron, M.A., D.Sc, F.E.S. 



(Technical Assistant, Entomological Branch), 

 Department of Agriculture, Ottawa, Canada. 



(Plate II.) 



The following is an account of an investigation into the life-histories and habits 

 of the species of bot-flies (Gastrophilus) occurring in the western provinces of Canada. 

 The investigation was undertaken co-operatively by the Entomological and Health 

 of Animals Branches of the Dominion Department of Agriculture under the direction 

 of the Dominion Entomologist and the Veterinary Director General. The greater 

 proportion of the work, for which the authors are equally responsible, was carried 

 out at the University of Saskatchewan, Saskatoon, Sask., during a period of about 

 four months extending from June to September, 1917. Certain of the experiments 

 dealing with the penetration of the larvae of G. intestinalis into animal tissue were 

 commenced at Saskatoon, but were supplemented later in the same year by others 

 carried out in the Department's laboratories at Agassiz, British Columbia. 



Recognizing the scantiness of the knowledge pertaining to the early stages and 

 habits of the three common species of bot-flies, the authors had in mind in this work 

 the elucidation of several obscure points, more particularly relating to the hatching 

 of the eggs, the form and behaviour of the first-stage larvae, the specific regions of 

 the host selected by the different flies in ovipositing, and the manner in which the 

 persistent attacks of the flies affect their hosts psychically. 



When one considers how common these insects are, and that they have been known 

 to both entomologists and veterinarians for several decades, it is surprising to find 

 how inadequate is our knowledge of the species. Indeed, the theories regarding 

 the hatching of the eggs and the mode of entrance of the larvae to the alimentary 

 canal of the host have passed untested as genuine currency through the literature 

 from the earliest times until quite recently, when the important discovery of the 

 direct penetration of the skin of cattle by the ox-warble (Hypoderma), by Carpenter 

 and Hewitt in Ireland (1) and one of the authors in Canada (2), has been almost 

 paralleled by the significant results of Roubaud's investigations (3) in France. This 

 last author observed in his experiments with guinea-pigs that, when the recently- 

 emerged larva of G. intestinalis is brought into contact with the buccal mucosa, it 

 promptly burrows into the mucosa and lies immediately beneath and parallel to 

 the surface.. 



* Read before the Annual Meeting of the Entomological Society of America, Pittsburg, 

 Pennsylvania, U.S.A., 29th December 1917. 



(C478) Wt.P3/130. 1,000. 9.18. B.&F.,Ltd. Gp.11/1 A 



