#1
Swept from Carex by Llyn y Cwn, an upland lake above Cwm Idwal, North Wales, 16 August 2023. It keys to C. means using Fonseca 1968 RES Handbook. But the cercal plate, second photo, looks more like the drawing of C. intermedia in Gregor et al. Muscidae of Central Europe.
#5
John, I observed both intermedia and means in field. It seems to me that they are two different species. Fonseca gave only colour differences in his very good book. I agree with him that colour works reliable enough. Gregor et al gave also cercal plates, my test cerci are very similar or just the same. You have C. means.