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A Platycheirus male should have modified front legs with broad and flattened tarsi, which seems not to be the case here. (A few species don't, but their body colouration is different.) The antennae should be dark, not orange as in Melanostoma. So the latter genus is more probable indeed. As the abdomen is rather broad and tergites 2-3 are no longer than they are wide, I’d vote for M. mellinum.