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Sphegina is a very tricky genus! Ball & Morris (British hoverflies. 2013) write:
"There are three very similar species: S. clunipes, S. elegans, and S. verecunda. S. elegans has rather yellow than dark humeri. ... Separating females of S. clunipes and S. verecunda is difficult and requires careful examination of the wing venation."
S. elegans and S. clunipes are known to occur in Norway, S. verecunda isn't. I searched The World of Syrphidae (http://www.syrphi.../photo.php) that gives distribution maps for the species, and GBIF (http://www.gbif.o...SSUE=false) that cites only two observations from Sweden. The Hoverfly Recording Scheme (http://www.hoverf...a4c554c9c6) says about the biology of S. verecunda:
"The larvae have been found in the exudates from a sap run on Ulmus. It is found in wet shady situations in woodland and carr. Adults are found in shade, or dappled sunshine, usually close to wet areas or streams, and are occasionally found visiting flowers." That doesn't sound like Oslo...
If you caught the fly, you should consult a Syrphidae/Sphegina expert. Some literature is cited here: http://www.syrphi...d=Sphegina
Regards, Sundew