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There had been some taxonomic confusion around Ch. arcuatum and Ch. festivum in the past that was, however, solved by conservation of the names in use and a designation of neotypes for the species in 2001. (If you have a deeper interest, see https://www.biodi...1/mode/1up). So both Ch. arcuatum and Ch. festivum are good species, the first one appears yellow with black markings and the second one appears black with yellow markings. So yours is no Ch. festivum.
Unfortunately, there are hardly morphological characters to discriminate between the species in the "yellow group", the colouration is highly variable, and even the male terminalia are mostly uninformative (https://www.resea...characters). Nevertheless, if we follow the key by Van Veen (https://books.goo...&hl=de), we arrive at Ch. arcuatum. The decisive clue is the length of the antennal segments. The wings of the sister species Ch. fasciolatum should have a darker front margin. However, some experts allow such darkened wing parts also for Ch. arcuatum - see https://diptera.i...d_id=60720. So to cut a long story short, you should label your pictures Chrysotoxum cf. arcuatum to be on the safe side.
Regards, Sundew