Biological Control of Insects

it one were to tack on all of biological manipulations utilized or suggested for insect control, treatment might well require several volumes. Therefore, in view of available space and writer's experience, this paper will be concerned only with biological control of insects as effected by predators and parasitoids (natural enemies). Insect control by such factors as genetically determined host resistance to pest insects, autosterilization, and pheromonal manipulations of pest biology or behavior, will not be discussed. Nor will paper touch upon microbial control of insects or biological control of weeds by insects. These are highly complex subjects which deserve attention of appropriate specialists. In any event, biological control of insects as effected by predators and parasitoids is a sufficiently meaty subject to occupy allotted pages. The author belongs to that group which adheres to a broad concept of biological control of insects. This is concept of Stern et al (77) and DeBach (13), which defines biological control as the action of parasites, predators, and pathogens in maintaining another organism's population density at a lower average than would occur in their absence. This describes a natural phenomenon-the regulation of a species' numbers by natural enemies. There is no stipulation that biological control involve man's manipulation of natural enemies, but on other hand definition accommodates this possibility. The current paper will treat two major aspects of biological control: classic and naturalistic. The paper will not meticulously examine all of recent literature. Instead, critical publications, both old and new, will be cited as they relate to matters bearing on present status of biological control of insects. Finally, discussion will concentrate on developments subsequent to 1960, which marks end of period treated by comprehensive volume Biological Control of Insect Pests and Weeds (12).