Athalia bicolor

This species is associated with buttercups and true to form, this one was found on a buttercup flower.

Athalia bicolor, North Elmham Cathedral Meadows (Norfolk, UK), 2nd June 2021

This one was also found on a buttercup. It differed slightly from the RES key in that the distance between the antennal sockets was not at least twice the distance between the eye margin and the antennal socket - only about 1.7x (but that's closer to 2x than the alternative option which is "about the same as"). Also the costa is not entirely black - there is a little orange at the base. I don't think these differences matter too much in view of the number of positive characters (e.g. black tergite 1, very short hairs on head, clypeus width exactly equal length of first and segments of fore tarsus (both 0.77mmm), etc. The orange base to the costa is evident in other photos of this species.

female Athalia bicolor showing wings, side of abdomen, hairs on top of head, face measurements, clypeus width, length of basal segments of foretarsus and saw, Wendling Beck Environment Project (Norfolk, UK), 17th May 2024