Athalia circularis

The old RES key has this as Athalia lineolata which is, I think, a synonym of circularis. I note from sawflies.org.uk that this species may in fact be a complex of species differentiated by foodplant.

This one (swept from among Bluebells) was keyed using the RES key. Until I examined the saw I wasn't convinced which way to go at the couplet that eliminated cordata - at some angles the clypeus looked very shiny and the hairs were hard to see which suggested cordata, but at other angles you could see plenty of hairs (albeit never as dense as on the labrum). The underside of the thorax had a broad orange centre - more than I would expect for cordata where it should be "entirely or almost entirely black" - so this pointed more towards circularis. The shallow teeth on the saw cleared up the confusion - far too shallow for cordata and spot on for circularis.

female Athalia circularis showing wings, underside of head/thorax and close-up of clypeus and labrum and two zooms of the saw, Wendling Beck Environment Project (Norfolk, UK), 30th April 2022

This one came to light in my garden. Again I had to look carefully at the clypeus - the hairs were obvious enough but sparser than on the labrum and elsewhere on the face, and the background was shiny. The extent of orange under the thorax was similar to the individual above.

female Athalia circularis showing hair around ocelli, relative size of gaps between antennae and eye, clypeus and labrum, forewing and saw with close-up of central teeth, North Elmham (Norfolk, UK), 13th August 2024