Thinonoma atra

This came to light and was the first beetle I identified using Duff's new volume 2, but I'm afraid I didn't find it straightforward. I completely failed to key it successfully so resorted to flicking through the whole Aleocharinae section comparing pictures of the spermatheca. Arguably the best match was Dacrila fallax but the beetle did not look like that species. Tachyusa concinna spermatheca looked a bit like my specimen's but again my specimen did not resemble that species. Thinonoma atra was also quite close and this time it did resemble my specimen - indeed I couldn't see any reason why it was not this species save for the fact that the spermatheca shape wasn't quite the same (the diagram in Duff lacks such a pinched in section in the sinuous long bit, and the point where it changes direction is nearer the middle). There are a couple of images of atra spermatheca at the Swedish Which Species? website (Vilken Art?) and these both show a more squashed in section and on one of them this is positioned much like mine.

female Thinonoma atra showing head from above, front and side, pronotum side, abdomen from below, abdomen from above, tergites after clearing, basal sternite after clearing and spermatheca (3 angles), Wendling Beck Environment Project (Norfolk, UK), 18th August 2024