Insect herbivores have been assumed to be more abundant in agricultural habitats than in native habitats; however, this hypothesis is rarely tested explicitly by comparing Þeld populations of domesticated plants and their wild ancestors. This study examined the abundance of the sunßower moth, Homoeosoma electellum (Hulst), and its parasitism by natural enemies in agricultural and native sunßower habitats. Nutrient levels and plant population factors in the two habitat types were measured to identify factors associated with the patterns of herbivory and parasitism. Adult male and larval H. electellum were consistently more abundant in agricultural habitats. In contrast, parasitism of H. electellum was 6 Ð10 times higher in native sunßower habitats than in agricultural habitats. Also, fewer parasitoid species were found in agricultural habitats, and parasitism by individual parasitoid species was reduced by 90%. Larval densities per ßower head were higher on agricultural plants, but parasitoids failed to respond to the higher densities. The relationship between ßower age and larval infestation differed between agricultural and wild ßowers; larval age tracked agricultural ßower age, but on wild ßowers, larvae moved from older to younger ßowers. Among the three nutrients sampled, only nitrogen was positively correlated with habitat differences. These results indicate that patterns of trophic interactions varied by habitat type and were related to plant phenotypic changes and environmental habitat factors such as crop domestication, nitrogen fertilization, and plant phenology.