Ophonus puncticeps

This is a difficult genus to identify. I've experienced some challenges and have now re-identified one individual which I originally showed on this page, albeit laden with caveats as I was aware there were some problems with calling it puncticeps. I now think it was rufibarbis, having compared the specimen with one each of what I think are puncticeps and rufibarbis. I have caught a few Ophonus which I've had to leave unidentified and whenever I've checked the genitalia they've turned out to be females.

One of the challenges for me in identifying the genus comes in interpreting the pronotum shape. Duff says rufibarbis/schaubergerianus etc. have, "Pronotum wider, as wide as the elytra at the humeri" vs. puncticeps, "Pronotum narrower, almost quadrate and usually clearly narrower than the elytra at the humeri". Well, that sounds simpler than it is in practice, at least for me. I'm assuming when it refers to pronotum width it means the maximum width of the pronotum, not the width at the base where it's adjacent to the elytra - but is that right? Having looked at a bunch of photos of both species I'm not convinced I can make out the differences.

This one was examined at the same time as two which I eventually identified as rufibarbis. Like those, it was a female so I couldn't confirm the ID with reference to the genitalia, but I am fairly confident. There was only one (long) bristle protruding from the side of the pronotum (4 on the rufibarbis).

female Ophonus puncticeps showing side of pronotum, North Elmham (Norfolk, UK), 14th August 2021

I re-examined another puncticeps I examined at the same time but this unfortunately lost its label so I'm not entirely certain which one it was though I think it was one of two Ophonus I caught in July 2018 (one of which I put down as puncticeps and the other I left unidentified).

This one was swept in an area where there was lots of Wild Carrot - puncticeps is apparently often found on Wild Carrot.

Ophonus puncticeps, Cranwich Camp (Norfolk, UK), 17th July 2021