fruit fly sterilization studies in Hawaii more 
than a dozen years ago. Studies of other 
scientists, demonstrating that radiation induced 
dominant lethals in competitive mobile sperm 
without necessarily destroying their ability 
to fertilize the ova, furnished an explanation of 
why our first results were even more promising 
than we had expected. 
REQUIREMENTS OF THE METHOD 
Requirements that determine the feasibility 
of application of the sterile male release 
method to insect populations, as developed by 
Dr. Knipling,+ are as follows: 
(1) Availability of a method of inducing 
sterility without serious adverse effects on 
mating behavior and competitiveness. 
(2) Method of rearing the insect. 
(3) Quantitative information on natural popu- 
lation density at the low level in the popula- 
tion cycle, 
(4) A practical way of reducing natural 
populations to levels manageable with sterile 
insects, 
(5) Information on rate of population in- 
crease as a guide for determining the neces- 
sary rate of overflooding with sterile insects. 
(6) Cost of current methods of control plus 
losses caused by the insect must be higher 
than the cost of reducing the natural population 
plus the cost for rearing and releasing the 
required number of sterile insects. 
(7) If complete population control cannot be 
maintained because of reinfestations by mi- 
grating insects, or new introductions, the cost 
of maintaining complete control by continuing 
sterile insect releases must be favorable in 
relation to the costs for current methods of 
control, plus additional losses caused by the 
insect. 
(8) There would be justification for em- 
ploying the sterile insect release method, even 
if it were more costly than current ways to 
control or eradicate insect populations, if it 
provides advantages in overcoming hazards to 
man and his environment. 
(9) Sterile insects to be released must not 
cause undue losses to crops or livestock or 
create hazards for man that outweigh the 
benefits of achieving or maintaining popula- 
tion control. 
96 
With undiminished repeated applications of 
sterile males, the ratio of sterile to normal 
insects becomes increasingly greater. Theo- 
retically with effective overflooding, eradica- 
tion of a species should be accomplished in 
four generations, according to the calculations 
of Dr. Knipling. 
Some qualification of the requirement that 
the sterile male release method cannot be used 
if the released sterile insects are harmful 
to crops, animals, or man may be in order. 
Federal and State plant pest control officials 
are often confronted with the need to eliminate 
an incipient infestation of a newly introduced 
pest species that sometimes involves com- 
paratively few insects. Such infestations could 
be overflooded effectively with numbers of 
sterile insects so small that the injury they 
would inflict could not cause appreciable harm 
or would be tolerated in the public interest. 
Insects that reproduce by asexual means, 
such as aphids, do not lend themselves tocon- 
trol by sterile insect release methods. As 
indicated in the above requirements, the sheer 
abundance of certain pests may prevent suc- 
cessful use of sterile males unless such in- 
sects can be brought within reach of the tech- 
nique by the use of population thinning agents, 
such as insecticides, cultural control, strong 
attractants, biological control, or other means. 
A basic limitation on the use of the method 
is inability to rear the pest insect whether 
artificially or on natural diets. The need to 
develop efficient methods for mass-rearing 
species for which all other requirements are 
met cannot be overemphasized. 
THE INSECT PROBLEM 
In 1952, approximately 10,000 species of 
insects in our country were important enough 
to be called public enemies in the Yearbook 
of Agriculture. About four-fifths of these are 
injurious to plant crops, since they reduce 
yield, lower quality, contaminate market prod- 
ucts, or increase marketing and processing 
costs. The most recent estimates of losses 
caused by insect pests that attack these crops 
add up to more than $3 billion each year. Con- 
trol of insect pests with insecticides has con- 
tributed much to our national growth and 
agricultural economy, but there has been 
