Cladius pectinicornis

The tiny projection on the 3rd antennal segment helped to identify this sawfly, in combination with the distinctive form of the saw.

female Cladius pectinicornis showing sawsheath and cerci from below, saw, basal antennal segments and forewing, North Elmham (Norfolk, UK), 22nd August 2020

On this one both antennae had broken off at the base (after the short segments) when I came to examine it but I don't think it was missing any segments. I couldn't see any sign of the projections which, according to the RES key, differentiate pectinicornis from difformis, so it initially seemed to be Cladius difformis. I couldn't find any reference to how the saw differed between the two species but noted that this one looked exactly the same as the pectinicornis I had previously identified (above). Looking up difformis to check its status I find that it is now considered to be a synonym of pectinicornis. I assume that means the two "species" are now lumped and considered to be one and the same species (theoretically it could mean that they remain separate and what used to be pectinicornis is now known as something else, but I can't find anything that suggests that might be the case).

female Cladius pectinicornis showing forewing, antenna, sawsheath and cerci from below and saw, North Elmham (Norfolk, UK), 14th August 2024