none The studies were carried out in Potentillo-albae-Quercetum, Pino-Quercetum and Tilio-Carpinetum near Bydgoszcz and Torun (Poland) in 1987-89. Three aphid species on leaves of the brown oak, Quercus robur L., were investigated: Tuberculoides annulatus (HTG) (the dominant), Tuberculatus querceus (KALT.) and Phylloxera coccinea (HEYDEN). The parasitoid guild of T. annulatus consisted of two aphidiid species (Hymenoptera: Aphidiidae): Praon flavinode (HAL.) (the dominant) and Trioxys pallidus (HAL.) as primary parasitoids, and four hyperparasitoid species: Pachyneuron aphidis (BOUCHE), Aphidencyrtus aphidivorus MAYR, Alloxysta sp. and Dendrocerus carpenteri (CURTIS). The forest type was of no importance to species composition of parasitoid guilds, but the dominance structure varied. Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Habitat; Terrestrial habitat; Land and freshwater zones; Palaearctic region; Europe Hymenoptera; Hemipteran hosts; Phyllaphididae; Hyperparasitism; Community structure; Forest and woodland; Poland; Bydgoszcz & Torun, parasitoid & hyperparasitoid guild, forest Phylloxera coccinea; Tuberculatus querceus; Tuberculoides annulatus (Aphidoidea ); Hymenopteran parasites; Parasitoid & hyperparasitoid guild; Plant hosts; Quercus robur (brown oak); Hyperparasitism; Forest and woodland; Poland; Bydgoszcz & Torun; Hymenopteran parasitoid & hyperparasitoid guild, forest