Ernobius pini

This species is substantially scarcer than Ernobius mollis, so was not expected here. I think the few Norfolk records are from the Brecks and NW Norfolk. However this specimen, which I examined together with my only Ernobius mollis so far, proved to be pini. The emargination of the fourth tarsomere of the tarsi, examined on both hind tarsi, clearly extended over more than half the tarsomere length - although maybe not quite as far to the base as the diagram in Duff. To see this more clearly I removed one tarsus and cleared it in potassium hydroxide - and my impression of the extent of the emargination appears to be confirmed. For extra reassurance I examined the shape of the fore tibia. This isn't described for pini in Duff, but is used to separate mollis from gigas - so it wouldn't confirm pini, but it might rule out mollis. Compared to the mollis I had just examined, it was not so clearly outcurved at the apex - perhaps ever so slightly so but it was more-or-less straight. That gave me more confidence that it wasn't mollis, and indeed I then realised that Hackston describes it as straight in pini.

Unfortunately I wasn't able to see the differences in the pronotal texture that are described by Hackston. I wasn't too worried about this, but decided to check the genitalia of both this and the one from 2020 I had identified as mollis. This confirmed my identifications of both beetles. There was a bit that came out with the aedeagus that also differed from the equivalent bit of the mollis - I'm not sure what this bit is - maybe one of the internal apical tergites or sternites? Anyway, a photo of it appears below.

Ernobius pini showing both hind tarsi (with close-ups of one before and after clearing), aedeagus and bit that came out with the aedeagus, North Elmham (Norfolk, UK), 9th August 2023

My photos of the live beetle above make it look paler than the specimen looked. Indeed, compared to the Ernobius mollis, this was clearly a different colour - darker more mahogany-coloured. It was also substantially smaller, but although the top and bottom end of the size range for pini is smaller than the top and bottom end of the range for mollis, the range given for mollis is vast and this was within the bottom of the range. As for the colour, mollis is described as variable so I'm not sure this was relevant to the ID either. In any case, here are the two beetles side by side. Note that the angle both beetles are tilted makes it looks like the top beetle is farther away, but in fact the photo was taken from directly above and both beetles are the same distance from the camera.

Ernobius pini, North Elmham (Norfolk, UK), 9th August 2023 (above) and Ernobius mollis, North Elmham (Norfolk, UK), 8th August 2020 (below)