Tachyporus tersus

I wasn't sure about this when keying it using Hackston. To be fair it does key to tersus but I'd struggled to see the microsculpture where it should be present so not being able to see it didn't convince me. I came back to it after Duff was published and using this it also keys to tersus. I had managed to see some microsculpture on the other Tachyporus I'd just examined (hypnorum and pusillus), albeit mot much and only when using the compound microscope, but I couldn't make any out at all on this one. I couldn't easily see all of the setae but I could clearly see one (distal) inner discal seta on both elytra, as well as (for example) two mid discal setae and at least one sublateral seta. I could not see any hint of the humeral seta or basal inner discal seta on either elytron. Although the elytra length was below the bottom of the range for hypnorum this wasn't by much of a margin so I wondered if it might possibly be that, however the aedeagus was very different to the hypnorum I had just examined. None of my references show what the aedeagus of tersus should be like, so it isn't confirmed genitalically. Supporting characters seem to include the darkness of the maxillary palps (at least the penultimate segment was darkened) and the breadth of red on the abdominal tergites.

male Tachyporus tersus showing side of elytra, maxillary palps, abdomeinal tergites, elytron and aedeagus (3 photos, last one on right with Tachyporus hypnorum on left), North Elmham (Norfolk, UK), 2nd May 2021

The next two were examined just after a pusillus and I was able to get a reasonable look at the elytral setae. I was content that all the correct ones were present and none of the incorrect ones were present. I also checked the measurements and these were in line with the key and (unlike on the pusillus) the elytral microsculpture was not visible even under high magnification. The lateral setae on these and pusillus always look more obvious than I expect prior to dissection which make me hestitate about whether I might have mistaken a hypnorum, but when I look at the elytra laid flat on glass they look much less impressive and quite different from how hypnorum looks when examined the same way.

female Tachyporus tersus showing lateral elytral setae from below, abdominal tergites, elytra, and head including maxillary palps, North Elmham (Norfolk, UK), 9th April 2023

The other one was a male and its aedeagus was slightly larger than that of the tersus above (though still much smaller than the hypnorum's). I couldn't detect any significant differences from the other tersus apart from size but I don't know how they compare to pusillus or most other species in the genus.

male Tachyporus tersus showing maxillary palp, lateral elytral setae from below, abdominal tergites, elytra, and aedeaus (last photo shows this one on the right and the one from 2nd May 2021 on the left), North Elmham (Norfolk, UK), 9th April 2023