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Dear Hartmut,

It is quite similar to Terellia tussilaginis in appearance, though it belongs to a different genus. It's a species of Chaetorellia. I don't know which species, for I have no list of the US at hand. All species look very much alike. There is a very common European species C. jaceae, but at this moment I can't tell you whether that species has been introduced to the US or not. I'll have to look into my literature for that.

Best wishes,

John Smit