KAKI 
STAIE ri^AiNT BOARD 
E-468 
UNITED STATES DEPARTMENT OF AGRICULTURE 
BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 
DIVISION OF INSECTICIDE INVESTIGATIONS 
THE HISTORY OF THE USE OF DERRIS AS AN INSECTIDE. 
PART II-THE PERIOD 1919-1928 
By 
R. C. ROARK 
Washington, D. C. 
February 1939 
