Araniella opisthographa

One of several very similar species collectively known as Cucumber Spiders. I have seen the vernacular name Twin Cucumber Spider used for this species but that doesn't appear to be in widespread usage. Identification relies on examination of mature male palps or mature female epigyne.

I had previously identified a female of this species based on what I thought was the epigyne but didn't manage to get photos of the epigyne and subsequent experience looking at other Araniella led me to doubt whether I had correctly interpreted what I was seeing. With that old record relegated to the dustbin this male becomes my first fully identified example.

Having collected numerous Cucumber Spiders in the past and concluded that they were mostly immature as I was unable to make out either male palps or female epigyne, I now only collect them if I can see what look like mature male palps. Well in this case I was mistaken as the spider moulted after I had collected it, indicating (I think?) that it was not quite mature when I collected. After moulting though, it bore a fine pair of palps. Here it is when I collected it:

maleAraniella opisthographa, Wendling Beck Environment Project (Norfolk, UK), 7th May 2023

By 23rd May (but possibly well before this) it had moulted. Now a mature male I was able to examine the palps to identify it. Several elements of the palps seem to differ between the species (the other common one being Araniella cucurbitina). I don't know what all the bits are called so I won't attempt to describe them, but the three views here are at different focuses which show different characteristics present in the diagram in the Collins field guide.

maleAraniella opisthographa, Wendling Beck Environment Project (Norfolk, UK), 7th May 2023