Stenus impressus

I found this on Rhododendron under Sweet Chestnut, Sycamore & Oak in a small woodland. I used Lott & Anderson to key this at the same time as examining a very similar insect that keyed the same way right up to the final couplet, between impressus and aceris. I would have liked to have checked both identities with reference to the genitalia but unfortunately both were female, however I am fairly confident they were not the same species. On this one I was able to see, under high magnification, reticulate microsculpture on tergite 3 whereas I could not make this out clearly on the other. Lott & Anderson refer to a possible difference in the colour of the knees. I'm not sure if there "knee" extends to the apex of the femora but on this one the femora (on all legs) was only slightly and narrowly darkened at the apex, whereas the other had much more obvious and extensively darkened mid and hind femora at the apex.

female Stenus impressus showing head & pronotum, basal abdominal tergites, hind leg, hind tarsi and spermatheca, Ling Plantation, North Elmham (Norfolk, UK), 16th October 2021