Protapion trifolii

Duff's key requires Protapion's to be "almost glabrous" which threw me as there are short white hairs all over the underside and the elytra. Hackston's key doesn't include such a constraint, but does refer to a furrow on the underside of the head which is sharply-bordered at the sides. There were numerous transverse furrows or wrinkles and one central longitudinal furrows on the underside of the head but the latter was weakly-defined and I wouldn't say it was sharply-bordered at the sides. So it took me a while to convince myself that it really was Protapion, but once that was sorted (everything else came to a swift dead end) it went to species quite easily. I caught 2 Protapion fulvipes at the same location (different spot there) and the differences in leg colour were very obvious.

Protapion trifolii showing step between pronotum and elytra and hairs on underside and elytra, Wendling Beck Environment Project (Norfolk, UK), 29th April 2023

I had a bit of a problem keying this one to genus too. Compared to the diagram in Duff, and also my previous experience of genus Protapion, the angle between the elytra and the pronotum (in side view) was much gentler. This led me to key past Protapion to genus Eutrichapion, but once there I hit a dead end. Turning to Hackston, it was a longer and more complicated path but it did lead me to the right place (which by this time I was already suspecting), genus Protapion. Using Duff to key it to species it was straightforward enough, though the gaps between some punctures on the pronotum were wide enough to consider the unlikely schoenherri. I was pretty sure it was going to be trifolii but checked Hackston which mentioned an additional character, a longitudinal furrow towards the back of the pronotum. Mine had this clearly enough (though only obvious from certain angles) which clinched it as trifolii. It was found in a pitfall trap (in propylene glycol, so no live photos).

Protapion trifolii showing close-ups of head/pronotum and elytra base, rostrum and antenna, fore tibia and tarsus and rear/side of elytra, Wendling Beck Environment Project (Norfolk, UK), 29th to 31st March 2024