Cephus pygmeus

Wheat Stem Borer Cephus pygmeus

The only member of this family that I've found so far, the first found on a buttercup in a wet meadow during the daytime and the second on Cow Parsley.

There was a slight angle between the saw sheath and the oblong plate, but in the photo it isn't perfectly side-on and I think this has exaggerated it. Characters pointing to pygmeus rather than spinipes include the subapical antennal segments being broader than long, the hind tarsi being black and the shape of the claws.

Wheat Stem Borer Cephus pygmeus showing wings, tip of antenna, saw sheath and claws, Wendling Beck Environment Project (Norfolk, UK), 14th May 2022

With the one above still fresh in my mind, identifying the next one was much quicker and easier.

Wheat Stem Borer Cephus pygmeus showing claw, saw sheath and tip of antenna, Ryburgh Road, North Elmham (Norfolk, UK), 1st June 2022

There were several Cephus feeding in flowerheads on Foulden Common - I retained three for species identification and all were pygmeus. I'm not sure how obvious it would be if I had found one of the other non-Cephus members of the family so I keyed them all to genus as well as species. Some of the characters shown below were used to get them to genus. The sawsheaths of the females did not narrow towards the apex anywhere near as much as shown in Fig. 85 in the old RES key but they were narrower than the apex of the hind tarsus and other characters checked out for Cephus ok.

female Wheat Stem Borer Cephus pygmeus showing antennal segments 1-4, claws, relative distances between antennal sockets and tentorial pits and sawsheath, Foulden Common (Norfolk, UK), 27th May 2023

The second female - this one was paired with the male below.

And the male paired with the female above.

female Wheat Stem Borer Cephus pygmeus showing antennal segments 1-4, claws, relative distances between antennal sockets and tentorial pits and underside of abdomen tip, Foulden Common (Norfolk, UK), 27th May 2023