none Recent evidence indicates that characteristics of both host plants and herbivorous insects influence attack of herbivores by natural enemies. The authors assessed experimentally the effect of fruit density of Cornus amomum (fruits/m super(3)) on percent parasitism of a specialist frugivore, Rhagoletis cornivora) (Diptera: Tephritidae), by Opius richmondi (Hymenoptera: Braconidae). They also examined correlations of parasitism by O. richmondi with number and density of R. cornivora (larvae/m super(3)) in the plant. Results indicate that spatial distribution of R. cornivora) larvae is related to risk of parasitism. Rate of parasitism of R. cornivora declined from 66.7 to 18.2% over the active season. These spatial and temporal relationships may have influenced the searching and oviposition behavior of R. cornivora .