Discoveries begin with bafflement. I thought I was reasonably familiar with all the British species of Olibrus; I’ve certainly seen all 7 of the species on multiple occasions. But I found myself baffled when trying to identify some Olibrus specimens collected at Sandwich Bay on the night of Friday 31st August going into the early hours of Sat 1st September.
The key to Olibrus species relies heavily on the presence or absence of microsculpture on head, pronotum and elytra. The microsculpture can be hard to see when it is present, so it is often difficult to be sure that it is absent. So ‘route one’ for me is to dissect, hoping for males, and match up to the genitalia drawings in the RES Handbook. I had four specimens and when I dissected them on Tuesday, they all turned out to be female, clearly of two species, and could not be identified by matching to the genitalia illustrations alone. So I keyed them out and they all came to Olibrus affinis. Bafflement begins. Presumably I’ve made some mistake somewhere, perhaps failing to see microsculpture? I put them aside to come back to on the following day.
I must admit that even on Tuesday evening I was wondering whether I might have found a species new for Britain. But this is a guilty thought – the proper response is to investigate every other possibility first. Am I even sure it is an Olibrus?! Is there any chance it could just be an aberrant individual of one of the other species? After a few hours on Wednesday morning comparing my Sandwich specimens to dissected and confirmed specimens of all the other British Olibrus species, I was sure I had affinis and one specimen of something new to Britain. But what?
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Ideally, it would be good to have an identification guide to the Olibrus species that occur on the near continent in northern France and the Low Countries. But in such situations, the best thing available is usually “FHL” (Die Käfer Mitteleuropas by Freude, Harde and Lohse) covering Germany and environs. And using FHL, I reckoned the only thing that fitted my specimen was Olibrus norvegicus. This species was added to the Mitteleuropas list sometime between 1967 (FHL volume 7) and 1992 (FHL volume 13) and was added to the Dutch list in 1985 but whether it was overlooked before or has recently colonised these areas I don’t know. Either way, it sounds like the sort of species that might be expected to turn up in Britain.
At this point, I decided I needed a male specimen to be certain, so I drove back to Sandwich Bay yesterday afternoon. After bumping into Paul Brock and chatting for a bit, I spent a couple of hours sweeping the grassland and dunes here. I reckon I saw many more Olibrus at night but this trip yielded 104 specimens, mostly affinis but with one male and two female norvegicus. The male is a good match to the genitalia illustration of norvegicus in FHL, so I’m now pretty confident that’s what it is. But I’d still like to compare it to confirmed norvegicus specimens, and/or get an expert opinion. If you can help, please get in touch.
It has to be said that bafflement is a pretty frequent feeling when I’m trying to identify beetles. Mostly the investigation just reveals that I’ve made a mistake, or occasionally that the author of the keys has made a mistake. But I love making discoveries so I’m always hoping that a bit of bafflement will lead to something like this!
This part of Sandwich Bay is a Kent Wildlife Trust reserve and permission to collect invertebrates on the site (which is a SSSI) can be obtained from them. Thanks to Greg Hitchcock of KWT for arranging permissions for attendees at the Coleopterists’ Meeting.