Limnobaris t-album

Several of these weevils were swept from sedges and as I didn't immediately recognise them I thought I might cut some corners keying them by running them through the ObsIdentify app. I would never rely on this entirely, even if (as was the case here) it was 100% sure about the identify. but it can help point you in the right direction. With 100% certainty the app said Mecinus pyraster, although to be fair to the ObsIdentify team the app does provide some caveats, not least when it comes to geographic coverage which I think is focussed on the Netherlands. It's not often wrong when it's 100% certain so I turned straight to the Mecinus key in Duff and it seemed to key pretty much straight to pyraster - well, nearly. There was one problem at the end - pyraster has pitchy or reddish tarsi whereas the other species in the last couplet (janthinus) has black tarsi - the tarsi here were black (except the claws) but other characters for janthinus didn't match (it even had the distinctive sudden apical expansion of the antennal scape of pyraster). There was another problem. When I was checking the tarsi colour I noticed the claws seemed well-separated to their bases - Duff's introduction to Mecinus mentioned that they should be basally connate. I sometimes struggle to tell if claws are basally connate or not, but these didn't seem to be. A quick Google search of images of Mecinus pyraster turned up some very similar-looking insects - provided I only looked at the ones showing the dorsal view! My insect had a dense covering of whitish scales on the sides of the abdomen, and the mesepimera, extending less densely onto the underside of the abdomen. These were clearly visible in side view but in all the photos of pyraster they were totally black. Did Mecinus even have raised mesepimera visible from above? No... these aren't Mecinus... back to the drawing board!

Starting where I should have started before, with Duff's Curculionidae family key, these keyed very straightforwardly to Limnobaris. Separating the two species was a little trickier - on the first one I looked at the elytral scales mostly didn't overlap but in one or two places they seemed to slightly. That insect was a female so I couldn't take it any further, but fortunately the second one I retained was a male. The elytral scales were shorter on that so I was pretty sure it would be t-album and the aedeagus confirmed it.

male Limnobaris t-album showing close-up of elytra and aedeagus (flat with all components, and side view of the main component), Wendling Beck Environment Project (Norfolk, UK), 25th April 2022

It is tempting to assume the female was the same species, especially as I was leaning towards t-album anyway based on the length of the majority of elytral hairs. But the male's hairs were shorter, both species are found on sedges and I think dolorosa is better recorded in Norfolk, so I guess it's plausible that both species are present here and on my current knowledge I don't feel sufficiently confident that the female was definitely t-album.

probable Limnobaris sp., probably Limnobaris t-album showing close-up of elytra, Wendling Beck Environment Project (Norfolk, UK), 25th April 2022

I feel a bit more confident about this female, swept from the same location about 3 weeks later. Not only were the elytral scales very short but the shape of the pronotum was convincingly good for t-album vs. dolorosa. Duff doesn't give any female genitalic characters - I'm not sure if that means they're not helpful for ID but in case they might be of some use I'll include photos here.

female Limnobaris t-album showing close-up of elytra, genitalia (including close-up of spermatheca) and size, Wendling Beck Environment Project (Norfolk, UK), 14th May 2022