UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 597 X 
Contribution from the Bureau of Entomology 
L. O. HOWARD, Chief 
Washington, D. C. PROFESSIONAL PAPER. April 9, 1918 
SOME BIOLOGICAL AND CONTROL STUDIES OF 
GASTROPHILUS HAEMORRHOIDALIS AND 
OTHER BOTS OF HORSES.’ 
By W. E. Dove, Scientific Assistant, Insects Affecting Domestic Animals. 
CONTENTS. 
Page. | Page 
[EDGR LH CTT ns ee ea 1 | Seasonal history of Gastrophilus............- 15 
Brief life history of Gastrophilus..-.....--.-- 2 | Gastrophilus haemorrhoidalis (Linnaeus) .... 16 
ERIS TONICHIP EOE ene a ok ons - ce etmesceasis 2 | Gastrophilus nasalis (Linnaeus) .............- 30 
Species differentiation ........-.-.---------- 3 | Gastrophilus intestinalis (De Geer) ..........- 32 
Distribution in the United States and prob- Effect of death of host upon Gastrophilus 
Apledispelrsiones mass ss-2 <2 255225---- > 5 laTyce ese n wane eae cette ma deee oaks comes aces 34 
Larval collections and rearing technique-.. 5: Controlishu dies seer ss eee Seer ee see 35 
Larval infestation and injuries..-...-..---.-- 6.) \SuUmmManyese sees as seas Sas eee e Seer 48 
Bothy annOyaNCGres 2/5. 5522 -<-ssie sce 13 4|Bipliozraph yao <2 Setsesere os teieeca eee 50 
Natural protection of horses......-..-------- 14 
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 haemorrhotdalis, 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 
1Mr. H. B. Bradford made the drawing illustrating the eggs of Gastrophilus, and 
Mr. W. N. Dovener made those illustrating the larye and dorsal aspects of the adults, 
Many of the photographs were made by Mr. A. K. Pettit. 
11216°—18—Bull. 597: 1 1 
