Dineura virididorsata

This sawfly gave me some problems keying it out. Firstly, although I suspected it was Tenthredinidae from the off, the unequal spurs on the front tibia suggested otherwise. They weren't just a little bit unequal - the longer one was getting on for twice as long as the shorter one. But it clearly wasn't a Wood Wasp (Siricidae) which is where I ended up taking the spurs to be unequal. I wondered if I'd gone wrong interpreting the straightness of the hind edge of the pronotum, a couplet which I find confusing as I'm never convinced I'm looking at the right bit. That took me to Pamphiliidae which was supported by the ObsIdentify app's best efforts (which frankly weren't very helpful). But keying it as a Pamphiliid got nowhere! So assuming it was a Tenthredinid after all, the key to genera took me to Dineura. I should have stayed there, but my initial investigation of Dineura found a load of photos of individuals with completely black heads that didn't really look much like my sawfly. Even some photos of virididorsata didn't look like mine - which I later realised was because they were all females. So having already been in doubt over the family, I started down a wild goose chase of re-keying before I eventually gave up and turned to Andy Musgrove for advice. He pointed me back to Dineura, and then the key quickly and clearly took me to virididorsata. By this time there was no real doubt remaining, but especially when the path to the ID isn't straightforward it is always reassuring to find the aedeagus confirms the ID, as is the case here.

male Dineura virididorsata showing wings, front tibial spurs and aedeagus, North Elmham (Norfolk, UK), 17th May 2022