Dicheirotrichus obsoletus

Dicheirotrichus obsoletus and the similar Docheirotrichus gustavii are both halophilic species found in saltmarshes, seashores and estuaries. Finding one in my North Elmham garden (mid Norfolk, 15 miles from the nearest coast) was therefore quite unexpected. I believe gustavii is the commoner of the two species but judging from records on the NBN Atlas, obsoletus is perhaps more prone to wandering inland (at least there are more inland dots on the map including at Shotesham and Weeting in Norfolk).

This individual was identified as Dicheirotrichus on account of the absence of an abbreviated scutellar stria. There was a vague hint of a short stria between the first and second striae near the scutellum, one one side only (perhaps an even fainter suggestion of one on the other side but in a slightly different position). I'm not sure if this would count as a scutellar stria as it's not inside the first stria, but in any case Duff's key does not require it to be completely absent - it only has to be more or less obsolete (and for the alternative option, if the striae are "somewhat reduced" then the elytra must also be glabrous which clearly wasn't the case here). The elytra were covered in hairs throughout, eliminating placidus and cognatus (placed in a separate genus Trichocellus in Duff and Hackston but I think this is now considered to be a subgenus within Dicheirotrichus).

Working out whether it was obsoletus or gustavii was trickier. It looks like both species are variable in overall colour but if I understand rightly gustavii is commonly (usually?) much darker than mine wherease obsoletus is normally tawny like mine, however if colour is useful at all I don't think it's diagnostic. There are photos of gustavii online (assuming they are captioned correctly) that look a lot like mine. The main difference appears to be the number of punctures on the inner elytral intervals, "mostly with one or two rows of punctures" on gustavii and "mostly with three rows of punctures" on obsoletus. The punctures are rather shallow and are not arranged in tidy rows, so judging this isn't totally straightforward, however I would say that on mine there are extensive areas with three rows, as well as a few with two, but none (except where the first striae narrows near the base) where there is just one row. On that basis I think I'm right in calling it obsoletus, though as always I welcome feedback.

Size may also support the ID as obsoletus. Hackston puts the top end of the size range at 7.5mm for both species but Duff allows obsoletus (but not gustavii) to go up to 8.0mm. Mine is 7.7mm long.

Dicheirotrichus obsoletus showing absence of abbreviated scutellar striae (2 views), elytral punctuation/hairs (5 views) and front tibia, North Elmham (Norfolk, UK), 9th September 2023