Posted by Graeme Lyons , Saturday 8 October 2011 15:00

Alice presented me with this little crab spider last week. She found it in her hair upon returning from a day's work at Filsham Reedbed so I thought I would have a go at identifying it. I recognised it as being in the genus Xysticus but there are twelve species and need to be seperated by their genitalia. With spiders, this is all on the outside but the female's genitalia, the epigyne, is (for me at any rate) far harder to distinguish than the male's genitalia, the palps. I think this is because the palps are more complex and it is easier to observe variation between more complex structures than simple ones.
I have only ever seen one species, Xysticus cristatus and I identified that from a male specimen. Knowing that this was from a wetland and reading that there was a swamp specialist in the genus (ulmi), I gave it a go. Here is the epigyne, I think it is just the common species cristatus but this just goes to show how hard I find them. I am not confident enough to put it to species. Xysticus sp. it is then. No ticks for me and from now on I will concentrate on the males.

2 Response to "Epigynes"

threecubes Says:

Yes that's X.cristatus. Xysticus are not easy, you really need a reference collection of named specimens to compare for accurate identification. X.ulmi is possible from Filsham so it's always good to double check any future hitchhikers on Alice when she's been to Filsham!

Andy Phillips

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