Abstract
Considerable evidence substantiates the idea that native pests can be controlled by parasites and predators of allied species and genera. In a survey of 66 pest species, which were successfully controlled by biological means and for which the habitats of all species could be verified, it was found that 39% were controlled by an introduced parasite or predator of an allied species or genus. Although relatively few attempts have been made to control native and imported pests with parasites and predators of species allied to the pest species, the proportion of successes is surprisingly high. Employing these species has certain advantages, especially in the control of imported pests, because no ecological homeostasis has evolved and the association between the parasite and host (predator and prey included) is new.