Acupalpus dubius

Apparently this is one of our commonest Carabids, but these are the first one I've come across.

This species is supposed to have a small puncture in the third interval in the apical third (according to Duff). Well, I could see the puncture, just, but it wasn't quite in the apical third. Not far off, and the alternative couplet required no puncture at all, so I'm sure this was the correct choice (I did check both ways just in case). In Hackston's key the position of the puncture is "beyond the middle" which is fine.

Acupalpus dubius, North Elmham Cathedral Meadows (Norfolk, UK), 31st May 2021

These two came to light. The pronotum seemed paler on the dead specimen than it did in life, prompting some uncertainty as to which way to key it. In the end I was happy that they were this species and that I could rule out the other options with a brighter red pronotum. I would have liked to havce confirmed it with reference to male genitalia but neither obliged by being the correct sex.

female Acupalpus dubius showing pronotum, elytra and internal sclerites, Wendling Beck Project (Norfolk, UK), 23rd June 2026

second female Acupalpus dubius showing pronotum, Wendling Beck Project (Norfolk, UK), 23rd June 2026

This third individual arrived with the last two. Unfortunately it had a bit of an accident as I closed the pot, resulting in it breaking in half, so no live photos. It was clearly different from the two above in that it had a more obviously pale pronotum, which prompted me to consider whether it might instead be Acupalpus parvulus. But some references suggest parvulus should have at least a dark centre to the pronotum and more obvious pale patches at the base of the elytra, and some photos of dubius online show just as pale a pronotum as this one has. The sides of the elytra were pale too, which is shown in several photos of dubius but I'm not sure how often parvulus shows this, if at all. So my working assumption is that this is another dubius. The only thing that slightly concerns me is that most photos of dubius only show one basal segment of the antennae pale (though the second is often intermediate sometimes) whereas this, like many photos of parvulus, has two segments clearly paler than the rest. Unfortunately it was another female so could not be confirmed genitalically. It is difficult to measure size when it's broken in half, but this was roughly 3mm long. The first photo below was assembled by placing the elytra as close as I could to the pronotum - they are not joined hence the unnaturally long neck.

third female Acupalpus dubius (presumed) showing head and pronotum, pronotum and elytra, Wendling Beck Project (Norfolk, UK), 23rd June 2026