Halidamia affinis

This sawfly, caught in my garden moth trap, keyed to male Periclista albida, but as it was a female I realised this must be wrong. It resembled Halidamia affinis and ignorning the relative lengths of the antennal segments it would key to this common species, but on Halidamia the third antennal segment is meant to be longer than the 7th to 9th combined, and on this specimen it was slightly shorter.

Halidamia affinis showing the 7th-9th segments of the antennna above the third segment of the other antenna in the last photo, North Elmham (Norfolk, UK), 17th May 2021

This one was seen resting on a Garlic Mustard leaf and duly potted for identification. Again I made the third segment of the antenna marginally shorter than the 7th to 9th segments, but only fractionally so, so I think it could count as "as long as". The forewing was 5.4mm long. It was another female.

Halidamia affinis showing wings (including close-up of vein A3), hind tarsal claws and both antennae, Wendling Beck Environment Project (Norfolk, UK), 13th April 2024