Hypsosinga pygmaea

When trying to identify this very small spider that looks (to me at least) very similar to some Linyphiid species, I made the assumption that it was a Linyphiid, and spent some time unsuccessfully trying to match the palps with the diagrams in Roberts volume 2. Thankfully, among the addenda to volume 1 at the end of volume 2, there are some diagrams showing variation in the palps of Araneus diadematus. I noticed some similarities on my first look through, but my spider was nothing like Araneus diadematus so I ignored this at first. But the more times, and the more carefully, I looked through the whole volume, it was increasingly clear that the palps in front of me really were much more like Araneus than any of the Linyphiids in the volume. Could it be Araneidae?

Turning instead to the Collins guide and the chapter on Araneidae, I fairly quickly homed in on Hypsosinga pygmaea. That was interesting: while I was failing to get anywhere with Linyphiidae I resorted to running photos through ObsID. When it wasn't returning Diptera suggestions, one of the few spiders it did suggest (with low % probability) was Hypsosinga pygmaea. I'd looked it up and dismissed it as all the photos I found on an initial search showed bold pale stripes through the abdomen. The plate in Collins does too. Mine had no such stripes - the abdomen (and carapace) were uniformly black. But reading the text it became clear that some males do have entirely black abdomens. I'm not sure how frequent it is - I guess it's the minority given the paucity of photos of such individuals online.

maleHypsosinga pygmaea (immature in first 3 photos) showing carapace from side and pedipalps (3 views), Wendling Beck Environment Project (Norfolk, UK), 17th April 2025