Bronze Ground Beetle Carabus nemoralis

The Duff key differentiates between this species and Ridged Violet Ground Beetle Carabus problematicus by the way the hind angles are raised above the level of the pronotal disc in problematicus but flat or slightly deflexed in nemoralis. I have found this confusing - even misleading - and I'm wondering now if it might have lead to the misidentification of some of the individuals shown below. If you look at the side view photo of problematicus at ukbeetles.co.uk the hind angles drop down from the side margin to a level that is lower than the highest central part of the pronotal disc. The similar species section at the bottom of the UK Beetles website clears things up a bit with a photo comparison of problematicus vs violaceus (the hind angles are not supposed to be raised in violaceus either). If I understand correctly, it would be more accurate to say that on problematicus the rear of the side margins of the pronotum turn up to a level that is higher than the rear of the pronotal disc.

Now I have identified this possible source of error two things make me wonder if I have identified all of the following nemoralis. Firstly Duff says that althoguh nemoralis is frequent in pitfall traps, it's rarely found by hand searching - and none of these were in pitfall traps. Secondly the UK Beetles describes nemoralis as "Adults are distinctive and unmistakable" but although inexperience is surely playing a part, I did not find, and based on the photos am still not finding, these especially distinctive and unmistakable.

Of the four beetles I had put down as nemoralis, I now think two are indeed nemoralis, and two may well be problematicus, but I would welcome opinion from Coleopterists with more experience than me. For now I have left all four on this page.

Although I only have the single photo to go on now, I think this one looks ok for nemoralis. The three rows of fovae on the elytra are very clear and I think the overall colour and shape of the beetle are ok for nemoralis.

Bronze Ground Beetle Carabus nemoralis, Wendling Beck Environment Project (Norfolk, UK), 28th March 2022

This one had a damaged elytron. I find with these Carabus the colour tones of the elytra can vary according to light so I'm wary of basing too much on this, but I have six photos of this one and in all six the elytra appear bronzy-brown.

Bronze Ground Beetle Carabus nemoralis, Hilgay Fen (Norfolk, UK), 6th May 2016

The next two I am no longer convinced by. I wonder if I may have been misled by the desciption of the pronotal hind angles and whether these might in fact be problematicus.

Although not apparent in these photos, this individual showed a strong purple reflection on the sides of its pronotum. The length was 21-22mm.

Bronze Ground Beetle Carabus nemoralis or Ridged Violet Ground Beetle Carabus problematicus, North Elmham Cathedral Meadows (Norfolk, UK), 9th May 2021

Bronze Ground Beetle Carabus nemoralis or Ridged Violet Ground Beetle Carabus problematicus, Bodney (Norfolk, UK), 14th March 2020