Quedius cf. nigrocaeruleus

I found this in a pitfall trap and keyed it to Quedius nigrocaeruleus using Lott & Anderson. None of the couplets leading to this identification seemed to be doubtful, but I'm conscious that this is a relatively uncommon species and I was not able to confirm it genitalically as it was female. Moreover I then tried to key it using Duff and although nothing in there eliminated nigrocaeruleus, Duff says that 11 species (including nigrocaeruleus) are only safely separable on male genitalia.

female Quedius cf. nigrocaeruleus showing head, side of head above left eye, pronotal microsculpure (at rear of pronotum), pronotum showing 3 dorsal setae and seta towards side behind latter), scutellum and elytra (2 views), Wendling Beck Environment Project (Norfolk, UK), 25th-26th September 2025

I found the next beetle upside down, moribund, on the toilet seat in my bathroom. Strangely I can't find any species of rove beetle with this listed as its typical habitat. Before Duff had been published I had all manner of difficulties keying it to genus, but eventually got to Quedius which seemed reasonably satisfactory - though I wasn't initially 100% sure that was right. Keying it to species within that genus I got to Quedius nigrocaeruleus, but I was far from convinced that was correct - indeed I suspected it was not.

I figured that if I was right in getting it to Quedius, then the relatively small eyes and confusedly punctate elytra with an even covering of hair place it in subgenus Microsaurus. The elytra was black, the first antennal segment was mostly black, the abdomen was black and both the head and pronotum had setae pretty much exactly where the setae that are important for ID are meant to be on nigrocaeruleus. However some of the other setae did not match those shown in the diagrams for nigrocaeruleus, for example I couldn't see the setae in the front half of the disc of the pronotum clearly.

I dissected it in hope of finding an aedeagus but the abdomen was devoid of any such aparatus so I assume it was a female. Unable to take it any further I retained it to re-examine later.

I looked at it again following the publication of Duff and was fairly satisfied that I had been correct in getting it to Quedius and probably correct in getting it to subgenus Microsaurus (although I wasn't convinced sg. Raphirus wasn't a better fit, but the first couplet in the Raphirus key was a dead end as the scutellum was both glabrous and punctured). The fore body length was around 5mm and the elytra edges were yellowish. One thing that was clear from Duff was that in order to get a certain ID I would need it to be a male, and as it was a female I don't think this can be resolved (although feel free to tell me if you think otherwise).

For the individual above I was satisified that according to Lott & Anderson it did key to nigrocaeruleus, the only real uncertainty about this being the ID being the fact that Duff implies females are not reliably identified. It therefore seems appropriate to label it as nigrocaeruleus but with the "cf." caveat. For this individual though there was a bit more uncertainty about that as I'd not been able to make out all the details leading to the provisional ID as nigrocaeruleus. I'm therefore not going any further than Quedius sp. as a label for this one.

female Quedius sp., possibly nigrocaeruleus, showing head (4 photos, the last showing the pair of setae (or their punctures) behind the eye), pronotum (2 photos, the second showing the side bristle), elytra, abdominal tergites (2 photos), abdominal sternites and cleared tip of abdomen, North Elmham (Norfolk, UK), 13th December 2021