Helophorus brevipalpis

Given how common some species are meant to be, it was perhaps a case of "about time too" when I found my first Helophorus. Identifying it was problematic, though after going through this experience the next ones were much easier. I initially used Andrew Duff's key and was immediately flummoxed at the very first line in the key. Describing the pronotal foremargin as "± straight" is a stretch, I think. It may be straighter than the alternative, but it is bisinuate with the fore angles protruding well forwards, so I really don't think it is accurate to describe it as ± straight.

My next problem came at the next couplet. I'm not sure if I've come across the term "intercalary striae" before, but I have come across beetles that have rows of less distinct punctures through the intervals between the main striae, and I assumed that's what was meant by the term. Mine did have a single rows of indistinct setiferous punctures through some of the intervals, so I took these to be the intercalary striae which took me off in the wrong direction again. It was only when I looked at Mike Hackston's key that it dawned on me. Hackston refers to "shortened scutellar striae next to the base of the first stria" (illustrated as strong shortened striae between the first and second striae) which my beetle clearly didn't have. That prompted me to look at Duff's glossary and all at last became clear. Duff distinguishes intercalary striae from the scutellar striae on the basis that it is between the base of the first and second striae, not between the scutellum and the first. Makes sense I suppose.

The beetle was about 2.7mm long.

female Helophorus brevipalpis showing pronotum, 3 close-ups of elytra, maxillary palps from two angles, head, apical sternite and underside, North Elmham (Norfolk, UK), 20th June 2023

These two came to light and were much more easily identified thanks to my experience with the one above. I was confident about the ID and discarded the specimens before checking a third Helophorus from the same trap. This proved to be a different species which started me doubting whether I'd got the first two right, and I wished I'd checked their genitalia for extra certainty. Fortunately I hadn't emptied my discard pot and after wading through a pot full of specimens I eventually found these. They were in fact quite obviously different in direct comparison with the third, much larger (the third was minutus) and with a different structure. Both proved to be females so I wasn't able to check the aedeagus.

female Helophorus brevipalpis showing pronotum, close-up of elytra and maxillary palps from side, Wendling Beck Environment Project (Norfolk, UK), 14th July 2023