This model indicates the great potential of an integrated program consisting of 

 conventional methods and the release of sterile insects. This becomes fully apparent 

 only by carefully noting the theoretical effect of each system when employed alone. 

 (Note models 2 and 3.) As previously shown, conventional control systems at the 90- 

 percent level for each generation would require treatments for 18 generations when 

 employed alone. The use of sterile insects alone would require the release of 45 

 million sterile insects during a period of five generations. However, by combining the 

 two systems in a completely integrated program, theoretical elimination of the popu- 

 lation would result from the application of conventional control methods plus 900,000 

 sterile insects for one generation, and the liberation of only 2,700,000 additional sterile 

 insects for three more generations. The two systems might be regarded as synergistic 

 in effect when combined for population control. 



It is emphasized that the models established are hypothetical, but the writer feels 

 that, in principle, they represent what we could achieve in practice. In order to put the 

 basic principles into practical use against a given insect problem, details of the biology 

 and behavior of the insect, the available methods of control, the relative costs involved 

 in each system, and other factors must be considered. 



We need to explore various new systems that will lend themselves to integration 

 with the sterile-insect procedure. The use of insect pathogens against immature stages 

 plus sterile-insect releases should hold much promise for the future. A combined 

 system of mass production and liberation of parasites and predators when the population 

 ishigh, gradually phasing into sterile-insect releases, conceivably could provide an 

 excellent combination. These two systems have principles in common. Both methods 

 would tend to become progressively more effective as the natural population declines. 

 When the natural population of the host is high, there might be a substantial increase in 

 the natural parasite population to augment the effects of those mass-produced and 

 released. It is the writer's view, however, that when the host population reaches a low 

 level, sterile insects will, for most species, be more efficient than parasites or preda- 

 tors . There is more and more interest in the development and use of attractants for 

 male insects. The integration of male sex lures and sterile male releases should hold 

 much promise. For example, if the males of an insect population are greatly reduced, 

 and are replaced by sterile males , the required impact on the reproductive potential of 

 the population can be achieved with fewer sterile insects. 



Important new developments are being made in the insect attractant field. Effec- 

 tive means of attracting insects by chemical or physical means might offer the possibility 

 of integrating the attractant and sterility principles without the necessity of rearing and 

 releasing insects. The trapped insects might be sterilized and released, thus increasing 

 the effectiveness of the trapping procedure. 



It is hoped that the discussion up to this point will be helpful in giving the reader a 

 better understanding of the principles and potentialities of the sterile-insect-release 

 technique, particularly when integrated with other control methods. Suggestions for 

 putting the sterility system into use for eliminating specific insects will be offered in 

 another section of this report. 



- 11 - 



