Rhantus suturalis

Brock's two photo guides on British insects assign this species the vernacular name Supertramp. I'm not sure how widely that is recognised.

When I first started making a concerted effort to identify most of the beetles that turned up in my moth trap, the majority of diving beetles were identified as this species. Since then they've dried up almost completed, whereas I am now getting regular Colymbetes fuscus which I did not find in the first couple of years or so. This made me wonder if I'd got my early IDs wrong, but although I don't have any specimens to check, the photos seem to be correct. I used Mike Hackston's key which I sometimes found a little confusing, thanks in part to not understanding how to sex them. Duff's key seems simpler in this respect - I just need to catch some more to see how well it actually works for me.

Rhantus suturalis, North Elmham (Norfolk, UK), 16th June 2017

Rhantus suturalis, North Elmham (Norfolk, UK), 10th July 2017

Rhantus suturalis, North Elmham (Norfolk, UK), 16th July 2017

Rhantus suturalis, North Elmham (Norfolk, UK), 17th August 2017

Rhantus suturalis, North Elmham (Norfolk, UK), 18th October 2017

Rhantus suturalis, North Elmham (Norfolk, UK), 24th October 2017

Rhantus suturalis, North Elmham (Norfolk, UK), 2nd August 2018

Rhantus suturalis, North Elmham (Norfolk, UK), 20th August 2020

This one was photographed well before I had access to resources enabling identification of diving beetles and was identified retrospectively a few years later when Brock's guide to Insects was published in 2014. However, despite the word "comprehensive" in this publication's title, suturalis is the only Rhantus covered by the book with no clue given to the existence of other species let alone how to separate them. At the time, therefore, the identification was best regarded as unsafe, although looking at the photo today I suspect it was nevertheless correct.

probable Rhantus suturalis, Bawdeswell (Norfolk, UK), 14th July 2008