Tenthredopsis friesei

This was one of two similar sawflies observed flying around a Pedunculate Oak tree. The identification was complicated by different references taking different taxonomic positions - The RES key by Benson does not recognise Tenthredopsis scutellaris, Lacourt synonymises friesei with nassata but recognises scutellaris, while the British and Irish Sawflies website recognises all three as distinct. The genitalia appears to eliminate other species but as far as I can tell does not help differentiate between these three. Size appears to be relevant but the different references disagree, presumably in part due to their different taxonomic stances - this one had a forewing of 10.0mm which depending on which reference you're using could be good or bad for friesei! In the end I think three characters point to friesei: 1) the colouration of the thorax, 2) the middle segmemts of the hind tarsus are whitish (well, not really white but obviously paler orange than the rest of the tarsus and the rest of the legs) and 3) the keel along the midline of the eighth tergite only extends to about half way down the tergite.

male Tenthredopsis friesei showing wings, hind tarsi, thorax from side, thorax from below, clypeus, apical sternite, eighth tergite, penis valve projection only just visible without dissection, geintal capsule and penis valves, Wendling Beck Environment Project (Norfolk, UK), 4th June 2025