Use of Insects for Their Own Destruction1

Abstract

In considering ways of controlling or eradicating insect populations, the importance of a fuller understanding of the population density in an area is stressed. Knowledge of the rate of increase of population from one generation to the next is basic to an understanding of the degree of control that is required to hold insects to noneconomic levels. Theoretical calculations are presented to show that a low-level mortality that is constant and superimposed on mortality produced by normal environmental resistance can in time lead to a greatly reduced population. The importance of applying control measures against the total population, rather than against segments of the population is pointed out. Four ways of using an insect species to destroy its own kind are: (1) The release of inserts made sexually sterile by gamma radiation, the only one that has already been employed successfully; (2) the use of chemicals that produce sexual sterility in the natural population of insects. The advantage of the desired type of chemical sterilants over chemicals that kill the insects is shown by theoretical trends in the population of a species subjected to the two types of control; (3) the release of adults infected with pathogens that would destroy larval progeny by transmitting the disease to other adults and contaminating the environment where the insect reproduces and develops; (4) the development and release of insect strains that carry deficient genetic characteristics. Such genetic deficiencies should be of a type that would not prevent rearing of the insect under controlled conditions or seriously interfere with the ability of the released males to compete with normal males in mating. Such genetic lethal factors would have to be expressed in the immature progeny or become lethal in the adult during hibernation.