Posted by
Sundew on 06-01-2019 19:35
#3
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
