Prionychus ater

Described as scarce and there aren't a huge number of records from Norfolk. Mine have all come to light, mostly in my garden moth trap.

This was the first I identified (though not the first I caught) and the ID was fairly straightforward. I nearly missed the ventrally-lobed penultimate tarsal segments as I was more used to tarsal lobes being visible from above, but the "ventrally" is a clue! Viewed side on the extension along the ventral side was perfectly clear.

The only character separating ater from melanarius that was at all doubtful was the elytral epipleura which were very slightly concave (partly accommodating the hind tibia). But they could hardly be described as "distinctly concave" and were nearly flat. The other characters checked out fine and the reticulate microsculpture on the pronotum and elytra was very clear under high magnification.

Prionychus ater showing hind tarus, prosternum, elytral epipleura, pronotal sculpturing and elytral sculpturing, North Elmham (Norfolk, UK), 22nd August 2023

The next two I examined were straightforward enough, though I wasn't entirely convinced about the proportions of the fourth antennal segment. Note that the photo of the tarsus shown below was taken at an angle that showed the ventral lobes most clearly and at this angle the pectinations on the claws are not visible - I can confirm that these were clearly visible at other angles!

Prionychus ater showing hind tarus, prosternum, elytral sculpturing, North Elmham (Norfolk, UK), 20th July 2022

Prionychus ater showing prosternum, North Elmham (Norfolk, UK), 10th August 2023

This one was in a meadow and also came to light.

Prionychus ater, Wendling Beck Project (Norfolk, UK), 11th August 2025

This came to light. I found it very hard to see the reticulation on the pronotum and elytra - it certainly didn't seem to be as clear as it is in some of the photos above, but there did seem to be a very vague reticulation and it was hardly shining. Eventually I found it a little more distinct on the disc of the pronotum. The elytral epipleura were slightly concave which is supposed to favour melanarius, but I wasn't convinced the texture was correct for that. Having previously struggled to make the proportions of the antennal segment 4 as they should be I wasn't surprised to have the same problem at first, but after measuring the width and length it was clearly a better match for melanarius. I'm never quite sure if you're meant to include the pedicel when measuring the segment length, but even if I didn't it wasn't right for ater. Then I realised that the ratio (the width specifically) depended heavily on the orientation of the antenna as the segments are not cylindrical. Rotated slightly so that the width was maximal, the proportions suddenly fitted into place for ater.

Prionychus ater showing hind tarsus from side, pronotum disc, prosternum, elytral epipleuron and antenna showing measurements of segment 4 at different orientations, Cooper Street, near Ash (Kent, UK), 17th July 2026