Brachydesmus superus

I found this in a pitfall trap but didn't manage to get any photos of it alive. My initial impressions were that it was smaller and more pallid than the otherwise similar Polydesmus species that I'd seen previously. The small size and 19 rings pointed to Brachydesmus superus, but to be certain I had to make sure it was mature. I couldn't find any gonopods so it wasn't an adult male, and at first I wasn't sure if I could see the epigynal flanges. There did seem to be something there, but it was dirty and I couldn't be sure. So I macerated in potassium hydroxide for a clearer view and then it became evident that it did indeed have epigynal flanges, so was a mature female.

Brachydesmus superus showing epigynal flanges in last three photos, Wendling Beck Environment Project (Norfolk, UK), 11th-12th May 2025