Diadromus pulchellus is a solitary endoparasitoid wasp that parasitizes the pupae of the leek-moth, Acrolepiosis assectella (Lepidoptera). Hitherto, every individual D. pulchellus from France that has been investigated was infected by an orthoreovirus, DpRV-1, and an ascovirus, DpAV-4. Recently, a new strain of D. pulchellus, established from a French field population, was found to be able to develop on leek-moth pupae, but lacked both DpRV-1 and DpAV-4. However, all these wasps were infected with a new cypovirus, DpRV-2. This cypovirus is transmitted to the A. assectella pupae at each wasp oviposition and is replicated mainly in the gut cells of the parasitized pupae. DpRV-2, like the ascovirus DpAV-4, is able to inhibit the defence reaction of A. assectella pupae and so contributes to the parasitic success of D. pulchellus wasps. Associations; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Immunology and repair mechanisms; Tissue reactions; Land and freshwater zones; Palaearctic region; Europe Acrolepiopsis assectella (Plutellidae); Hymenopteran parasites; Diadromus pulchellus; Parasitoid associated virus transmission to pupae & modulation of host defence mechanisms; Encapsulation; France; Tours; La Ville aux Dames; Hymenopteran parasitoid associated virus transmission to pupae & host defence mechanisms modulation Diadromus pulchellus (Ichneumonidae); Associations; Cypovirus (virus); Lepidopteran hosts; Acrolepiopsis assectella; Parasitoid associated virus transmission to pupae & modulation of host defence mechanisms; France; Tours; La Ville aux Dames; Parasitoid associated virus transmission to lepidopteran host & host defence mechanisms modulation none