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Field-collected populations of Aphytis holoxanthus DeBach (Hymenoptera: Aphelinidae) and of A. lingnanensis Compere were selected for malathion and azinphosmethyl resistance, respectively, utilizing the male selection method. In preliminary experiments, fertility of virgin females was not significantly lower than that of mated females, and the rate of development of their progeny was similar. Males proved more susceptible to pesticides than females, and among them the sons of virgins were more susceptible than the sons of mated females. Some after-effects of sublethal exposure to pesticides were noted in both species. A mating ratio of 1 selected male: 2.0-2.5 females was optimal. Cold storage of female pupae proved feasible for synchronizing availability.Resistance of A. holoxanthus to malathion was not increased by 25 male selection cycles. Resistance of A. lingnanensis to azinphosmethyl, which had already been improved by mass selection, was further increased by 7 cycles of male selection.The different outcomes of the two projects are discussed in relation to the variability of the original field populations, and the results of male selection are compared with those of mass selection of identical populations.