none Ascogaster reticulatus Watanabe castrates its host Adoxophyes sp. (Lepidoptera: Tortricidae). No gonads, male or female, develop in larvae that were stung as 0-d-old eggs. The parasitoid's effect on host development is time dependent. Delayed exposure of Adoxophyes sp. eggs to parasitoid attack increased the incidence of pseudoparasitism and abnormal gonads, and decreased the number of successfully eclosing A. reticulatus adults. Pseudoparasitized hosts were either completely castrated or they had abnormal gonadal growth. Comparisons of host/parasitoid interactions are made between A. reticulatus and A. quadridentata and their respective hosts, Adoxophyes sp. and Cydia pomonella L. Each parasitoid's development beyond the first stadium may depend on when its respective host commits to diapause.