Bembidion varium

Once I'd figured out this was in the genus Bembidion it keyed very straighforwardly to varium. My issue with getting it to genus was that the keys seem to think that all Bembidion have the third elytral interval the same width as the adjacent intervals, whereas on this (and judging from photos online, quite a few other Bembidion species) the third elytral interval was clearly broader than the other intervals, which, according to the keys, points to genus Bracteon. That got me a little excited briefly as neither Bracteon species appear to have been recorded in Norfolk before, but there were problems calling it Bracteon - it was too small for either species and the pattern on the elytra didn't seem to be quite right. Admittedly Hackston states that you need to be looking at the middle of the elytral intervals, and it was towards the base that the third interval was most obviously broad, but even at the middle I would say it was clearly broader than the second and fourth. And these third intervals did contain two pale spots that could be described, as Hackston does for Bracteon, as "containing two distinct opaque patches (silvery spots)". Duff doesn't specify the middle of the interval and given a choice of "Elytral interval 3 similar to the neighbouring intervals" (Bembidion) or "widened and with two dull patches" (Bracteon) I don't think it was unreasonable to head to Bracteon using either key. However, that word "dull" was problematic as I couldn't see any difference in shine between the pale spots in interval 3 and the rest of the interval, and also Duff adds for Bracteon that the length should be >5.5mm, which it clearly wasn't (it was 4.5mm).

Once I'd double-checked that I was in the right subfamily and hadn't gone wrong up to this point in the key, I then keyed it as Bembidion and then checked to see if other photos of varium online shared the wide third interval - which they do. Bracteon photos show an even broader interval 3, and this remains as broad beyond the second puncture. Another difference appears to be that in Bracteon the dorsal punctures are in the middle of the pale spots, whereas on this varium the dorsal punctures were in the dark areas not in the pale spots.

One character used in keying this that isn't shown in any of my photos was the epipleura of the elytra which were pale yellowish (helping to eliminate the darker-legged obliquum).

Bembidion varium showing elytral apex and rounded hind angles of the pronotum, North Elmham (Norfolk, UK), 22nd August 2024