Heteropteran predators in temperate regions encounter a portion of each year that is unsuitable for reproduction and development—generally winter and portions of the spring and fall. Many species of heteropteran predators pass this period in a state of diapause, the majority of species as adults. They typically overwinter as individuals in scattered, sheltered habitats, such as in leaf litter, under tree bark, or in winter grasses. Overwintering mortality has been studied in few species, but appears to be high. Among diapausing species, photoperiod appears to be a primary cue for diapause induction, although the effect of photoperiod may be modified by ambient temperatures, and, in at least 1 case, by the quality of prey. Sensitivity to diapause-inducing photoperiods occurs in either the nymph or the adult, or in some combination of the nymphal and adult stages. When sensitivity occurs in the nymphal stages, it is restricted to the later instars. Diapause in predatory Heteroptera is maintained by short photoperiod, or an interaction of short photoperiod and low temperature; conversely, long photoperiods and high temperatures contribute to diapause termination. Several species of predatory Heteroptera feed while in diapause; thus, prey availability may be important in selecting an overwintering site. Understanding diapause is valuable for commercial production, where diapause can impede rearing or be a valuable tool for storing or stockpiling predators.