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Photo#708850
Spider - Eriophora edax

Spider - Eriophora edax
Brown Canyon, Baboquivari Mts, Pima County, Arizona, USA
September 27, 2012

Moved to Eriophora edax - juvenile
Moved from Eustala. This is a pretty tricky one and I've been flipping and flopping on it for quite some time now. I gave it some hard consideration over the last few days trying to see something new that I hadn't considered before. Here is what I came up with. I think that in general Eustala has a rounded carapace in the eye region. Eriophora edax tends to have a carapace with a squared off front. Since juveniles of these two genera are easily confused... I'm using the shape of the carapace to determine genus. I'm not sure this is a reliable field marking for juveniles, but I feel it's fairly logical.

Compare Eustala then Eriophora edax carapaces here

 
Interesting discovery!
Will have to try this. Does it help us with 179229 and 724419?

Moved
Moved from ID Request.

....
Maybe something in Eustala? Lets see what the others think.

 
Eustala?
That would be my guess too. I haven't seen a pattern quite like this one before.

 
The shape is right
but the pattrn is very distinct

 
The ones with this pattern
have actually been placed in Eriophora edax

 
...
Aha, so the reference picture I used is possibly a misfile. Eriophora certainly looks like the stronger match.

 
The new one
without pattern also is in limbo between the two genera. Next time I'll collect one. We have literature at the UAIC that should get us to the genus, but not further

 
The Eustala you are most likely to encounter there
is E. rosae which has the dark pattern of your 616986. E cazieri is from southernmost Florida. This and the recent plain one are most likely Eriophora instead. The spider team should be working on these soon so we should be able to get confirmation. Can you give us the plant communities where you found these three specimens? It may help us understand them better. And you are correct, the ventral views of these two genera are very different. That would help significantly.

 
Grassland with Mexican Blue Oak riparian
along creek

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