Dorytomus longimanus

I potted this off a fencepost near a stand of poplars (Black Poplar hybrids I think). Unfortunately it was on its last legs when I photographed it so the pictures aren't the best. The beetle was 4.4mm long and I keyed it using Duff, straight after keying a Dorytomus tortrix from a different location. It looked quite different to the tortrix so I was surprised when it seemed to key to tortrix too. However the patterning on the elytra and overall colouration seemed to exclude that, but I couldn't see where I'd gone wrong in the key. Compared to the tortrix, it was much harder to see the shape of the foremargin of the prosternum so I tried keying it as if it was notched, despite being almost sure it wasn't. This led to melanophthalmus, but that didn't seem right either, and should be smaller.

Looking at Mark Gurney's guides, longimanus looked like a distinct possibility, although I wasn't convinced the forelegs were particularly long. In both Duff and Hackston this differentiates from tortrix by the length of the side of the prosternum compared to the diameter of the fore coxae. To my eyes it matches the diagram for tortrix, and comparing it side-by-side to the tortrix I'd just identified I still couldn't convincingly see any difference. But the more I investigated all the other possibilities, the clearer it seemed to be that it had to be longimanus. Nothing else fitted the shape and length of the rostrum, the long scales covering the genae from the prosternum and the overall colouration.

I dissected it to see if the genitalia might help confirm or counter this ID but it proved to be a female. In fact longimanus is the only Dorytomus whose spermatheca is shown at coleonet.de (and I don't have any other references showing spermathecae for other Dorytomus). This one was a pretty close match to the longimanus spermatheca shown at coleonet.de, and quite different from that of the tortrix that I had just examined. Both are shown together for comparison below.

female Dorytomus longimanus showing prosternum, scales at side of pronotum, apex of elytra, base of rostrum, side of prosternum, fore tibia, pronotum and rostrum, North Elmham railway (Norfolk, UK), 28th February 2024

Here is its spermatheca, on the right with that of the Dorytomus tortrix on the left.

spermathecae of Dorytomus tortrix, Bintry Mill (Norfolk, UK), 17th May 2023 (left) and Dorytomus longimanus, North Elmham railway (Norfolk, UK), 28th February 2024 (right)