Tenuiphantes tenuis

Formerly placed in the genus Lepthyphantes.

This appeared in a pitfall trap. Using the Collins guide this keyed to genus Lepthyphantes which of course tenuis was a member of when Collins was published. I had an inkling it might be tenuis based on a comparison of online images but all the references seemed to agree that you need to check the male palps or female epigyne for a certain ID. I couldn't make out enough detail of the epigyne initially so left the abdomen in some warm potassium hydroxide solution for a while to clear it. That improved things, but the abdomen was still full of gunk and visibilty still wasn't good enough. With a bit of gentle persuasion I managed to clear enough of the gunk out of the abdomen to see it properly. Even then I couldn't completely convince myself simply by comparing it with the diagrams in Collins, but after checking all the members of the genus at the Spiders of Europe website I was finally convinced.

female Tenuiphantes tenuis showing eyes + clypeus and epigyne (at various degrees of clearing and focuses), Wendling Beck Environment Project (Norfolk, UK), 17th-18th May 2023