Tenthredo amoena

This was potted off a Hogweed flowerhead. The RES key says this species should have an entirely yellow first segment of the antenna, lacking the dark fleck on the outer face that is present in distinguenda. However other characters pointed towards amoena. The Sawflies of Britain and Ireland website also suggests this species should have entirely yellow first segment, and Lacourt suggests that it's very rare for it to be marked with black. Taking this option in Lacourt also requires passing "fore and middle tibia often entirely yellow" which adds further doubt that this is the correct option as they're predominantly black on this individual. But some other photos of amoena appear to show yellow fore and mid femora so that doesn't seem to be a problem, and the mesopleuron is shiny with only shallow punctures; taking the other option quickly hits a clear dead-end. Lacourt also shows the saw and the teeth match this individual.

female Tenthredo amoena showing head from above and behind, antennal scape, tegulum, forewing, first tergite, fifth tergite and saw (at 3 zooms), Hoe Rough (Norfolk, UK), 11th July 2025