A bit tricky to tell in the image, due to the reflection and the slight graininess, but I think the bands are actually separate at the midline ... making it a match for Melangyna viridiceps ... but see my other notes ... could be M.collatus, so let's take it just to genus at this stage
I find it tricky to decide whether to take the safe option and leave something at genus level only, or take it to species knowing that I can't really see enough to be 100% sure. I often opt for the species name, but I don't have any problem if others prefer to leave something at genus only. In the major collections I've been fortunate to have access to, I've seen enough misidentifications and name changes to realise that nothing is set in stone.
I agree Kim - either approach is fine. And, yes, that's an important take-home message ... we don't have to be 100% confident to 'call' something, and identifications can always be reviewed in the future. Cheers!