Bledius dissimilis

This was caught in my garden moth trap alongside a larger, brighter Bledius opacus. I initially keyed it using Lott and went to dissimilis without any real concerns. However there were only 4 records of dissimilis in Norfolk up to 2021 (I don't know how many since), so I also tried taking it through Duff's key. Duff uses a different range of characters but again it keyed to dissimilis without any problems. The description matched well too, so I think this must be the correct ID. Duff warns that the trio of dissimilis, occidentalis and crassicollis are very variable and often only safely separable on male genitalic characters, but the character separaing dissimilis from the other two was so unambiguously clear in this instance (the elytra were very clearly longer than the pronotum) that I assume this one is safe to call in spite of it being a female.

I am not aware of differences between the spermathecae of the various Bledius species and the form of this one's spermatheca was very similar to that of the Bledius opacus that I'd identified immediately prior to examining this beetle.

female Bledius dissimilis showing foreparts, pronotum, elytra, tergites, fore coxal fissure and spermatheca, North Elmham (Norfolk, UK), 12th June 2025

I caught this one in the same trap the following night. Again it keyed to dissimilis using both Lott and Duff, but this time was a male complete with its long incurved teeth on sternite 7. This appears to be quite diagnostic, but I thought it might be useful to examine the genitalia while I was at it. I almost wished I hadn't as I had a hard time marrying the aedeagus up with the diagram in Duff. Despite this, I can't see how it can be anything else, and subsequent examples (see below) helped reassure me further.

male Bledius dissimilis showing antennae, head, pronotum (focussed on edge and on disc), fore coxal fissure, elytra, apical tergites, sternite 7 (in situ and isolated) and aedeagus (2 flat views, dorsal and ventral or vice versa, and side view), North Elmham (Norfolk, UK), 13th June 2025

This was one of two from a differernt location but also to light and just 3-4 days after the last two. I attempted to dissect the first one dry which was a bad idea, destroying it in the process so the aedeagus wasn't examined.

male Bledius dissimilis showing mandibles, head, pronotum, elytra, tergites and sternite 7 (in situ and isolated), Wendling Beck Environment Project (Norfolk, UK), 16th June 2025

I macerated the abdomen before attempting to dissect this one, as I usually do. The aedeagus shares the same difference from the diagram in Duff as the first male above, in particular the outer part (valvae? parameres?) is straighter-sided with a distinct angle, whereas in Duff it is shown as more evenly curved. However the interior parts are more clearly visible on this individual and I am reassured that these are exactly as shown in Duff for dissimilis, and perhaps just as importantly, unlike those shown in Duff for other species of Bledius.

second male Bledius dissimilis showing apical tergites, sternite 7 and aedeagus, Wendling Beck Environment Project (Norfolk, UK), 16th June 2025