Replacement of horses and mules by tractors on farms in the 
United States has been a steady and impressive process. But 
the process has been by no means total—in 1958 there were 
about 3,348,000 of these animals on farms in this country. 
In many areas, maintaining the health of draft animals con- 
tinues to be an essential part of farm management. Because of 
‘this fact, there is.a consistent demand for information about 
illnesses that affect horses and mules. A revival of interest in 
light horses has increased the demand. 
Prevention and treatment of the disorders caused by horse 
bots are problems that concern thousands of horse owners. To 
meet the demand for information on control of horse bots, the 
U. S. Department of Agriculture publishes this bulletin. 
Prepared by 
Entomology Research Division 
Agricultural Research Service 
Washington, D.C. Issued June 1959 
This leaflet supersedes Farmers’ Bulletin 1503, 
The Horse Bots and Their Control. 
For sale by the Superintendent of Documents, U.S. Government Printing Office 
Washington 25, D.C. — Price 5 cents 
