Ophonus melletii

I have really struggled to identify some of the Ophonus beetles that I've caught (at least those in subgenus Metophonus) but eventually settled on most of them being what's supposed to be the commonest species, Ophonus rufibarbis. Unfortunately all of those have been female so I haven't yet managed to confirm that species genitalically. Although I haven't really got to grips with the difference in pronotum vs. elytra widths, I have managed to differentiate these from ones that appear to be Ophonus puncticeps, some of which have been males. Of those two, this beetle more closely resembled the females I've identified as Ophonus rufibarbis. The number and arrangement of long hairs sticking out from the pronotum matched, and that seemed to make it a choice bewteen rufibarbis and schaubergerianus, although the beetle was a lot smaller than another apparent rufibarbis caught at the same time. I had my doubts, but prior to dissecting this one I suspected it would be another (small) rufibarbis.

Once dissected I was pleased to see that it was a male, but surprised to find that the aedeagus did not match rufibarbis at all. Instead it appears to be melletii, which I understand to be quite a rare species in Norfolk. Apparently melletii usually has a fine marginal bead along the base of the pronotum, at least at the sides. I was unable to see this even under 63x magnification. At some angles it looked like it might have a trace of one (as seen in the photo below) but viewing it at different angles I think this was no more than a slight change in texture and not a bead - and I can see something similar in photos of species that aren't supposed to have a bead. The other non-genitalic difference I can't make sense of is that it should have only one lateral trichobothrium on the side of the pronotum. I have spent long looking at the various hairs or setae that stick out from the side of the pronotum in this and other Ophonus, and the pits they emerge from, and compared these to high definition photos of various Ophonus online, and I have to say that if this species only has one trichobothrium then I am completely befuddled as to how to differentiate a trichobothrium from any other long hair.

male Ophonus melletii showing pronotum, elytra and aedeagus (side and flat views of whole and of tip), Wendling Beck Environment Project (Norfolk, UK), 21st June 2025