UNITED STATES DEPARTMENT OF AGRICULTURE 



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BULLETIN No. 597 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



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Washington, D. C. 



PROFESSIONAL PAPER. 



April 9, 1918 



SOME BIOLOGICAL AND CONTROL STUDIES OF 

 GASTROPHILUS HAEMORRHOIDALIS AND 

 OTHER BOTS OF HORSES. 1 



By W. E. Dove, Scientific Assistant, Insects Affecting Domestic Animals. 



CONTENTS. 



Page. 



Introduction 1 



Brief life history of Gastrophilus 2 



Historical 2 



Species differentiation 3 



Distribution in the United States and prob- 

 able dispersion 5 



Larval collections and rearing technique ... 5 



Larval infestation and injuries 6 



Bot-fly annoyance 13 



Natural protection of horses ,- 14 



Page. 



Seasonal history of Gastrophilus 15 



Gastrophilus haemorrhoidalis (Linnaeus) 16 



Gastrophilus nasalis (Linnaeus) 30 



Gastrophilus intestinalis (De Geer) 32 



Effect of death of host upon Gastrophilus 



larvae 34 



Control studies 35 



Summary 48 



Bibliography 50 



INTRODUCTION. 



In compliance with requests from farmers and horse breeders of 

 the Dakotas and Montana regarding " fly annoyance " to horses, a 

 survey of conditions was made in the autumn of 1914 by Mr. F. C. 

 Bishopp. Under the direction of Dr. W. D. Hunter and the super- 

 vision of Mr. Bishopp, investigations were undertaken in the follow- 

 ing summer upon the European Gastrophilus haemorrhoidalis, com- 

 monly known in that section as the " nose-fly." 



The preliminary investigations in the summer of 1915 revealed 

 the fact that the concentration of horses in pastures had rendered 

 breeding conditions practically ideal for bot-flies, and that a most 

 serious fly nuisance had developed which implicated three species of 

 Gastrophilus. This concentration of horses in pastures may be 

 attributed in part to the advent of gas engines, automobiles, and 

 tractors, and to maximum prices, which has encouraged the breeder 



1 Mr. H. B. Bradford made the drawing illustrating the eggs of Gastrophilus, and 

 Mr. W. N. Dovener made those illustrating the larvae and dorsal aspects of the adults. 

 Many of the photographs were made by Mr. A. K. Pettit. 



11216°— 18— Bull. 597 1 1 



