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Thank you Theo. The passage about host species was interesting. It says that immature stages has been found in nests of Vespa crabro (which the fly clearly resemble), but an english articel state that the only recorded host i England are Vespula vulgaris (in underground nests) http://www.bacoastal.co.uk/Entomology/2004-Volucella-zonaria.pdf
Do you know more about which host it use in the european mainland?