Atheta nigra

Having just spent hours unsuccessfully keying two other Aleocharine beetles using the new Duff volume, finally resolving them by comparing the spermathecae with the diagrams in Duff, I decided to go pretty much straight to the genitalia on the next two (all four came to light together in arable). This one, the smallest of the four, was a female and I quickly found a good match for the spermatheca. I did have a quick look through the description and attempted to reverse-key it to make doubly sure, but the spermatheca seems to be pretty distinctive.

female Atheta nigra showing head and pronotum (from above and side), elytra, mid tibia, maxillary palp, tergites, sternites and spermatheca, Wendling Beck Environment Project (Norfolk, UK), 18th August 2024