Ophonus rufibarbis

Sometimes I get identifications wrong when using keys and usually it's because I've made a mistake, either misreading something or more likely misunderstanding or misinterpreting something. Rarely (at least when it's Duff's and Hackston's beetle keys) is it because the key is wrong. But after spending far too many hours critically examining 4 Ophonus rufibarbis/schaubergerianus specimens carefully working through both Duff and Hackston keys, I have come to the conclusion that the keys are at least misleading in some respects, if not in some ways wrong. But perhaps I am still misunderstanding something and it is me, not the keys - if you think so, please let me know so I can learn!

Based on the puncturing on the pronotum disc and the elytra I initially identified my first 3 specimens as schaubergerianus. I had my doubts, not least because there are (or at least were) three times as many records of rufibarbis in Norfolk than schaubergerianus, so the odds of my first three (mostly in insignificant habitat) being schaubergerianus seemed low. My specimens were also all on the small side for schaubergerianus, giving me further reason to question them. But there seemed to be no mistaking that the puncturing on the pronotum and elytra put them as schaubergerianus and not rufibarbis. The clinching male genitalia were not available as they were all females.

I finally concluded that my fourth specimen, also a female, was rufibarbis, although it was extremely similar to the previous ones. I concluded that the pronotal puncturing clearly fits rufibarbis best. According to Duff the disc should be "very sparingly punctate, almost impunctate" on rufibarbis vs. "about as closely punctate as the pronotal margins" on schaubergerianus. Well the disc was clearly less closely punctate than the margins - the contrast was clearer than on the specimens I had examined previously. But it was not almost impunctate. The gaps between punctures were wide - but there were still plenty of punctures across the whole discal area, and these were deep, individually as obvious as the ones at the margins. If it had just said "sparingly punctate" I could have agreed, but "very sparingly punctate" I didn't think so and "almost impunctate", absolutely not. But the description for schabergerianus was unambiguously wrong - the disc was quite clearly more sparingly punctate than the margins. Hackston's description of the pronotal punctures is a little simpler: "much sparser towards the middle than the sides." for rufibarbis vs. "not markedly sparser on the top than at the sides." for schaubergerianus. The difference between the sides and centre was clear enough on this specimen to fit his descritpion for rufibarbis much better than schaubergerianus. On balance the pronotal puncturing was clearly wrong for schaubergerianus as decribed by both Hackston and Duff, and pretty much right for rufibarbis as described by Hackston. Not quite so right as it's described by Duff but still closer to his description of rufibarbis than for schaubergerianus. So based on this character alone I feel comfortable calling it rufibarbis.

But there remains a problem with the elytral punctuation. Both keys describe the differences in elytral punctuation similarly: 2-3 rows of punctures on the inner intervals for rufibarbis and mostly with 4 rows on schaubergerianus. The punctures aren't arranged in particularly tidy rows so this isn't always easy to assess, but although there were clearly only 3 punctures in a loose row in some places, there were clearly 4 in some places, even 5 sometimes. There's a high quality image of rufibarbis by Udo Schmidt at Flickr. The puncturing on the 4th interval outwards is easiest to see and there are clearly 4-5 punctures wide in places here, but does the 4th interval count as one of the "innter intervals"? Probably not, but that begs the question, what exactly do Duff and Hackston mean by the "inner intervals". Could they be specifically referring to the one and only one innermost interval on each elytron, i.e. the one adjacent to the suture, or do they mean any of the intervals that are relatively close to the suture, i.e. including the second and perhaps the third intervals at least. I think the latter is a better understanding of the words used, at least as I understand the English language - it's the difference between inner and innermost. The innermost intervals are the two adjacent to the suture, and the inner intervals include at least 1-2 of the next intervals out. But if the authors are referring only to the innermost intervals then this makes a big difference, and whether it's what they meant or not, based on the images I can find of the two species online I think it perhaps should be what they meant. Udo Schmidt's photo does show only 3 punctures in rows on the innermost interval, at least for most of the length. And the best quality photos I can find of schaubergerianus do seem to show 4 punctures on this innermost interval. So I think maybe the innermost interval is the only one that really matters here, not any of the other intervals that might be inclduded within a undefined description of inner intervals. And on my specimen, there are one or two places where there are four punctures across the innermost interval, but in these places the punctures aren't in anything like a straight line so it's questionable whether you could describe it as a row of four punctures. Where they are arranged in anything like rows they are only 3 deep. So in the end I think this does support the ID as rufibarbis, even if not precisely as described in the keys.

female Ophonus rufibarbis showing pronotum and elytra (2 views), North Elmham (Norfolk, UK), 10th August 2023

So now I'm looking back at the three I'd previously identified, albeit tentatively, as schaubergerianus (one was caught later but examined earlier). On these the contrast between the punctures at the disc of the pronotum and the sides was less clear, but they were less closely punctured on the disc than at the margins. At the time I didn't feel the contrast was sufficient, especially with Duff's description of "almost impunctate" but I think it probably is enough. And as far as I can see, the innermost interval does only have 3 punctures across at least for much of their length. The second and third intervals often have 4-5, but if I'm right in concluding that it's only the interval that's adjacent to the suture that counts, then this doesn't matter.

Duff distinguishes rufibarbis and schaubergerianus from melletii and subsinuatus by the number of lateral trichobothria on the sides of the pronotum - one each side for melletii and subsinuatus and two each side for rufibarbis and schaubergerianus. Mine have had 3 or 4 long hairs sticking out between the front and mid point of each side of the pronotum, all in a similar direction and much longer than the hairs covering the pronotum. I'd initially assumed these were all lateral trichobothria and that by saying 2 Duff means at least 2 and doesn't exclude 4 - and as where Hackston's key diverges on this character he says "2-4 bristles in the front half" for schaubergerianus and rufibarbis, I guess that's right. But the distal of the 4 bristles, the one at the middle of the edge, seems thicker than the others (if not longer) - so I wondered if it could it be that this is a lateral trichobothrium and the others are merely setae or bristles? I concluded not, as if I took them to have just one lateral trichothrium then all of mine would either be melletii (very unlikely - rare in Norfolk) or subsinuatus (only known in the UK from two specimens on Portland).

I think it's worth adding at this point that getting these down to a choice between rufibarbis and schaubergerianus wasn't altogether straightforward. I've been confused by the pronotum width and shape when eliminating puncticeps (indeed, I initially included one here which I had tentatively identified as rufibarbis but which I have now realised was puncticeps). I think I'm a bit clearer on this now, though I'm not convinced many of the puncticpes photos online quite conform to the pronotum being clearly narrower (I assume it means at its widest point?) than the elytra at the humeri, so I'm still not sure I've totally grasped what Duff's getting at here. In any case, it seems that puncticeps can be ruled out on the number of setae on the side of the pronotum.

female Ophonus rufibarbis showing pronotum and elytra, Wendling Beck Environment Project (Norfolk, UK), 21st August 2023

This was the first one I looked at, and I really struggled. I didn't really understand the pronotum size/shape characters and initially judged it to match puncticeps best, though with a low level of confidence.

Then I checked the Hackston key and realised that the number of bristles on the sides of the front half of the pronotum was wrong for puncticeps - it had 4 bristles on the side of the pronotum (the one at the middle being longest, the one at the front being shortest, hardly longer than the hairs on the upper surface).

I initially retained the specimen as I wasn't sure about the ID and later when I found two that I think really are puncticeps, I looked at it again. At 7.5mm long it was larger than the 2 puncticeps I examined at the same time and at this point I realised it was rufibarbis or schaubergeriana.

female Ophonus rufibarbis showing pronotum (from above and below showing the side-bristles) and genitalia, North Elmham (Norfolk, UK), 26th June 2020

This is the other one that I examined at the same time as the last one. The four bristles on the side of the pronotum were clearly different from the puncticeps I examined with them, and the contrast between the blacker elytra and redder head and thorax was very apparent. I initially thought the strongly punctured pronotal disc and the number of punctures on the inner elytral intervals eliminated rufibarbis but as described above I now think rufibarbis was the correct ID.

female Ophonus rufibarbis showing side of pronotum and centre of elytra, North Elmham (Norfolk, UK), 17th June 2022

Having been through all the pain of figuring out how to identify this species, the next one I identified was *so* much quicker to resolve. It was another female.

female Ophonus rufibarbis showing pronotum and centre of elytra, North Elmham (Norfolk, UK), 11th August 2023

These two turned up in my garden moth trap during an exceptional night for beetles (over 240 comprising 18 species). There was also an Ophonus puncticeps with them which provided a good opportunity to compare the two species. The pronotum was noticeably more punctate on the puncticeps. On both rufibarbis the discal punctures were sparser and shallower than at the sides. Both rufibarbis were females.

two female Ophonus rufibarbis both showing side of pronotum and pronotum from above, North Elmham (Norfolk, UK), 12th August 2024

Here are the last beetles either side of the male Ophonus puncticeps caught with them. Note that the puncticeps in the middle is slightly further back than the two rufibarbis - it was not shorter (at least barely so - they were all almost exactly the same length). You can see the difference in pronotum shape here - it looks noticeably smaller (especially narrower) on the puncticeps.

male Ophonus puncticeps (centre) between 2 female Ophion rufibarbis, North Elmham (Norfolk, UK), 12th August 2024