Effects of earthworms in soils of contrasting nitrogen content on a plant-aphid-parasitoid interaction were investigated in a greenhouse experiment. Presence of earthworms (Aporrectodea caliginosa) increased root biomass and carbon content of shoots of Cardamine hirsuta. The nitrogen content of shoots and roots was increased by earthworms, but only in the more enriched nutrient soil. Aphid reproduction (Myzus persicae) was enhanced by the presence of earthworms. Soil type, but not earthworm presence, affected the dynamics of the parasitoid wasp Aphidius colemani; the number of parasitised aphids was increased on plants growing in the enriched soil. Larger parasitoids also emerged from mummies of plants growing in this soil. Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Trophic structure; Habitat; Terrestrial habitat; Abiotic factors Aporrectodea caliginosa (Oligochaeta); Trophic structure; Impact on plant biochemistry & root biomass, above ground tritrophic interactions relations; Soil habitat; Chemical factors; Soil nitrogen content Aphidius colemani (Aphidiidae); Hemipteran hosts; Myzus persicae; Tritrophic interactions with host plant hosts, annelids impact on plants relations; Food webs Myzus persicae (Aphidoidea); Hymenopteran parasites; Aphidius ervi; Tritrophic interactions with plant hosts, annelids impact on plant chemistry & root biomass; Plant hosts; Cardamine hirsuta; Food webs none