Obviously, there is much that we do not know about the competitiveness of insects 

 reared under laboratory conditions and released into the natural environment. Changes 

 in behavior or vigor that develop in laboratory strains may affect their competitiveness 

 in the field and be independent of any adverse effects of radiation or chemosterilant 

 treatment. The behavior of laboratory-reared insects after release compared with the 

 behavior of the wild population may be one of the vital aspects for investigation in 

 developing the sterile-insect-release method for a given pest. Population geneticists 

 may be in a position to contribute materially in this field. Through selection, under 

 proper artificial environmental conditions, it may be possible to maintain field 

 adaptability and competitiveness in strains that are to be employed for release, or even 

 to develop strains that are better adapted and more competitive in a given environment 

 than the wild strain. For example, the screw-worm research group at Mission, Tex. , 

 under the direction of A. H. Baumhover, obtained encouraging laboratory results in 

 selecting a screw-worm strain that appears to be particularly resistant to starvation 

 (food and water) during the first few days after emergence from the pupal stage. 



Summary of Basic Requirements and Factors That Determine 

 the Feasibility of Employing the Sterile-Insect-Release Technique 



a. Availability of a method of inducing sterility without serious adverse effects on 



mating behavior and competitiveness . 



b. Method of rearing the insect. 



c. Quantitative information on natural population density at the low level in the popula- 



tion cycle. 



d. A practical way of reducing natural populations to levels manageable with sterile 



insects. 



e. Information on rate of population increase as a guide for determining the necessary 



rate of overflooding with sterile insects. 



f . 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. 



g. If complete population control cannot be maintained because of reinfestations by 



migrating 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. 



- 25 - 



