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This could also be D. postclaviger. To cite the Syrph the Net species account:
"D.postclaviger can be separated from the closely similar species D.friuliensis (van der Goot) and D.hilaris (Zetterstedt), using the keys provided by Haarto and Kerppola (2007) and Bartsch et al (2009). D.postclaviger is not included in the keys provided by van Veen (2004), where is would run down to D.friuliensis. The adult male is illustrated in colour by Bartsch et al (2009).

I hope you collected them.

Greetings, André