Gyrohypnus angustatus

This was found in a pitfall trap. I recognised it as a member of the tribe Xantholinini and keyed it using Lott & Anderson. I felt that the rear of the head was less rounded that members of the genus Xantholinus that I'd recorded previously, though I wasn't completely convinced about that. Keying it both ways I ended up with either Xantholinus longiventris or Gyrohypnus angustatus/wagneri. It wasn't obviosuly (at least obvious to me) wrong for longiventris which I'd seen a few times before, though it seemed to be a little on the small side which fitted angustatus/wagneri better. Lott & Anderson require the head to be strongly punctured behind the eyes for Gyrohypnus, with diameters of the punctures less than the distance between them. On this the head was strongly punctured, but the distance between the punctures varied, less than the diameter of the punctures just behind the eyes but more further back.

Fortunately it was a male and when I examined the genital capsule it was immediately clear that it was not longiventris, but did seem to fit angustatus pretty well. I had removed the genital capsule without the pair of apical structures (juxta arms?) which are shown attached to the capsule in both Lott & Anderson and Duff. I removed these separately and included them in the first genital photo below, though they are not positioned correctly in relation to the capsule (or each other - they diverged as I extracted them). The next photo of the genital capsule was taken in water and the internal structures match the diagrams in both resources. I moved it to alcohol and then euparal essence for a clearer view of the internal structures (last photo) but by this time some structures had become displaced slightly. The diagram for wagneri in Duff is quite different from the one in Lott & Anderson in terms of the internal structures, but I think the shape of the capsule, if not also its size, rule out wagneri anyway.

male Gyrohypnus angustatus showing elytra, head punctures, neck and aedeagus (with juxta arms, in water and in euparal essence), Wendling Beck Environment Project (Norfolk, UK), 11th-12th May 2025