To date, competition in spiders is generally assumed to be under bottom-up control through resource competiton. By relating parasitoid abundance rates in eggsacs of P. monticola to their own density and the density of a related congeneric species, I provide empirical data that apparent competition might be a strong, and previously neglected, interspecific competition mechanism in spiders that share a common parasitoid. Top-down interactions through shared enemies (here parasitoids) are subsequently suggested to be important for structuring natural predator communities in successive landscapes, in which species are promptly replaced by congenerics. It additionally suggests that empirical approaches of interspecific competition in spiders, and generalist predators in general, should focus equally on top-down and bottom-up approaches. BR Parasites diseases and disorders. Parasites. Insect parasites. Hosts. Ecology. Competition. Habitat. Terrestrial habitat. Land zones. Palaearctic region. Eurasia. Europe. Pardosa monticola (Araneae): Host; Pardosa pullata (Araneae): Host; Hidryta sordida (Ichneumonidae): Parasite. Hidryta sordida: Arachnid hosts, Pardosa monticola, Host specificity, Pardosa pullata, prevalence, Grassland, Sand dune grasslands, Sand dune habitat, Belgium, Flanders; Pardosa monticola, Pardosa pullata: Hymenopteran parasites, Hidryta sordida, Host specificity, prevalence, Interspecific competition, Grassland, Sand dune grasslands, Sand dune habitat, Belgium, Flanders. ST Animalia, Arthropoda, Arachnida, Araneae; Animalia, Arthropoda, Insecta, Hymenoptera, Apocrita, Terebrantia, Ichneumonoidea, Ichneumonidae. Arachnids; Arthropods; Chelicerates; Hymenopterans; Insects; Invertebrates. none