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Hi Paul, I do not know literature on the pupal state of syrphids - for the larvae I use Graham E. Rotheray (1993): Colour Guide to Hoverfly Larvae.
He says M. auricollis larva's prp (the posterior breathing tubes) has a basal rim while M. cinctella's is yellowish brown in overall colour.
Your darker larva is not unicoloured and seems to have a basal rim so I guess this could be M. auricollis.