Tachyporus hypnorum

I have several Tachyporus specimems that I need to return to, at least when Duff's relevant volume is published if not before. Most of them are, I think, hypnorum, but when I examined them I was concerned by the apaprent absence of microsculpture on the elytra which I understood was a key character of hypnorum. The exact wording in Hackston's key is "Elytra completely microscopically sculptured" which I assume means I should be able to see some microsculpture at least under high magnification. I have pended them for now in case Duff or another source provides more insight, but I shall be surprised if they don't turn out to be hypnorum given how common this species is supposed to be.

I examined this one a bit later and identified it as hypnorum despite the lack of clear microsculpture. In this case I could, just, see a vague hint of microsculpture on the elytra. It was far from clear and difficult to see at all, but maybe enough to qualify? Anywway, the other characters all seemed good for hypnorum, so I'm pretty confident it is.

Tachyporus hypnorum showing elytra and maxillary palps, Ling Plantation, North Elmham (Norfolk, UK), 6th April 2024

Now armed with Duff I'm less concerned about not being able to clearly make out the microsculpture - Duff suggests this requires 100x magnification and indirect lighting (I could just about make it out on this one using the compound microscope, at least near the apex). This one seems to tick all the boxes for hypnorum except I struggled to see some of the setae. Of these the one I really wanted to see was the humeral seta but I could not positively identify it on either elytron. The specimen had been in a pot for over 4 years and it was at least the second time I'd examined it, so it's entirely plausible that some of the setae could have come off - I could see what might have been a pore on both sides but I wasn't entirely convinced. None of my references provide diagrams for the genitalia for this species so I'm not sure if the aedeagus helps confirm or not. The forebody length (head to apex of elytra) was 2.0mm and the elytra was 0.99mm long. The internal sac sclerite (at least I assume that's what it was) was very short at 0.024mm long. The beetle had come to light.

male Tachyporus hypnorum showing maxillary palp, elytra (both, one at 2 focuses) and aedeagus, North Elmham (Norfolk, UK), 6th June 2020

I normally struggle to see all the elytral setae but on this one I could see too many! In the end I think it must be hypnorum but there were one or two contrary characters. There was what looked to me like an outer discal seta on one elytron, pretty clearly I would say, and that is not meant to be shown by hypnorum. It didn't appear to be present on the other elytron. The couplet in Duff where hypnorum and others split off based on the absence of an outer discal seta also requires the other option to have elytra to be less than 0.85mmm long. These elytra were 0.96mm long (excluding the basal tab where the elytra affix to the body - I'm never sure if you're meant to include it in the measurement or not), so surely way too big for the options with three rows of discal setae. I think there were one or two other setae that aren't shown in the diagram for hypnorum in Duff but I think some variation is ok - Hackston shows an extra apical seta for example (as did mine) compared to Duff's.

Other than the extra setae I think everything was ok for hypnorum. The lateral setae didn't seem as obvious as I'd thought with the previous hypnorum but I think they were long enough. The penultimate maxillary palp was also a little darker than I would have liked but I think I can still get away with calling it yellow. So on balance I think it must be hypnorum, but always happy to be corrected if you think I've got this wrong.

male Tachyporus hypnorum showing maxillary palps (2 views), abdominal tergites and elytra, North Elmham (Norfolk, UK), 3rd March 2022