Screwworm Eradication: Concepts and Re- 
search Leading to the Sterile-Male Method 
By EK. F. KNIPLING 
Entomology Research Division, Agricultural Research Service 
United States Department of Agriculture 
[With 6 plates] 
A NEW APPROACH to insect control is now being applied in the 
Southeastern United States to deal with the screwworm, Callitroga 
hominivorax (Cqrl.), one of our most damaging pests of livestock and 
game. ‘The procedure involves the use of atomic radiations to produce 
sexual sterility in millions of insects reared in an insect factory. The 
sterile serewworm fiies are then released against their own kind to 
defeat the primary purpose for their existence—reproduction. 
This unique insect-control program is being conducted by the Ani- 
mal Disease Eradication Division, Agricultural Research Service, U.S. 
Department of Agriculture, in cooperation with the Florida Livestock 
Board. It is the culmination of 8 years of pioneering research, 
both basic and applied, which was conducted by a group of Department 
of Agriculture entomologists with the Insects Affecting Man and 
Animals Research Branch of the Entomology Research Division. 
Utilizing knowledge of the effects of atomic radiations on insects 
and of screwworm life history, habits, and ecology, a method of bio- 
control has been developed which probably represents the ultimate in 
precision and efficiency. The research leading to this development has 
been described in a number of publications: Bushland and Hopkins 
(1951 and 1953), Baumhover et al. (1955), Lindquist (1955), and 
Knipling (1955). It will not be necessary, therefore, to discuss the 
details. fowever, it seems desirable to review the most significant 
features of the investigations and the control program now under way. 
It seems appropriate also to speculate on the place that the sterile-male 
method might have in the control of other major insect pests. 
SCREWWORM BIOLOGY, ECOLOGY, ECONOMIC SIGNIFICANCE, AND 
METHODS OF CONTROL 
The screwworm fly (pl. 1, fig. 1) is an obligatory parasite of warm- 
blooded animals. Eggs (pl. 1, fig. 2) numbering 200 to 300 are de- 
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