Enochrus nigritus

This keyed to nigritus using Duff, I think without any real hitches. I wasn't convinced about whether I could see a notch in the hind margin of the last sternite at first - but this became easier to see after giving the abdomen a spell in potassium hydroxide solution. I also checked it through Hackston but encountered a couple of issues here - one couplet demanded that it should be under 4mm (it was 4.2mm) and another that the last segment of the maxillary palps should be entirely black (vs. only darkened in the middle) - this segment was mostly dark, including the tip and the middle, but the base of the segment was paler. I think if I'd just used Hackston I would have ended up with nigritus based on a combination of characters, and the genitalia matched, but this time Duff got me there more straightforwardly.

male Enochrus nigritus showing head from front, tip of last sternite (before and after soaking in potassium hydroxide). maxillary palp (and antenna) and genitalia, Wendling Beck Environment Project (Norfolk, UK), 11th June 2023