Adaptation of native parasitoids to a novel host: the invasive coccinellid Harmonia axyridis

Abstract: In its introduced range, the invasive coccinellid Harmonia axyridis (Coleoptera:Coccinellidae) threatens many non-pest insects through competition and predation, and this raisesthe need for appropriate control measures to be investigated. One strategy could be to considerthe introduction of natural enemies (predators, parasites and pathogens) that regulate H. axyridispopulations in its native range. Indeed, escape from natural enemies is likely to have contributedto its invasive success (the so-called ‘enemy release hypothesis’). However, re-uniting H. axyridiswith its own enemies requires rigorous and time-consuming risk assessment to ensure there are nounwanted side effects on native species. Moreover, the introduction of alien enemies may beunnecessary if the organisms that attack native ladybirds in Britain also attack harlequins. Herewe present field data which indicates that two species of parasitoid wasp: Dinocampuscoccinellae (Hymenoptera: Braconidae) and Oomyzus scaposus (Hymenoptera: Chalcidoidea);and two species of parasitoid fly: Phalacrotophora fasciata and Phalacrotophora berolinensis(Diptera: Phoridae) may be adapting to H. axyridis in Britain as a novel and abundant host. Thismay provide some level of natural population control.