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Hallo, I just used one of the rare opportunities to take a photo of a living insect in that insect-poor times. I suspect it is 'Eristalis , that's why I post it here. If it is another family, would you please transfer it?

I was very surprised to see the mating couple change position several times, without leaving the leaf, they were sitting on. I watched the couple about one minute. It was already in copulation when I came nearer. I attach a photo from every position.
I would like to know, if this behaviour of changing position is normal in that species or in that genus. And of course I hope, you can identificate the species.

Germany, Baden-Württemberg, Dreifaltigkeitsberg near Spaichingen 48,083332° 8,76299° 990 m
at 9th May 2018 on leaf of Tilia