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Coras? - Amaurobius ferox

Coras? - Amaurobius ferox
Franklinville, Gloucester County, New Jersey, USA
June 20, 2013
Size: Approx. 6mm

Images of this individual: tag all
Coras? - Amaurobius ferox Coras? - Amaurobius ferox Coras? - Amaurobius ferox Coras? - Amaurobius ferox Coras? - Amaurobius ferox Amaurobius ferox? - Amaurobius ferox - female Amaurobius ferox? - Amaurobius ferox - female Amaurobius ferox? - Amaurobius ferox - female Amaurobius ferox? - Amaurobius ferox - female Amaurobius ferox? - Amaurobius ferox - female Amaurobius ferox? - Amaurobius ferox - female Amaurobius ferox? - Amaurobius ferox - female Amaurobius ferox? - Amaurobius ferox - female A. ferox - Amaurobius ferox - female

Moved from Hacklemesh Weavers.

She died ...
sometime last night or today. When I checked on her and saw she had passed I used some soft tweezers to put her in alcohol and her abdomen had already putrefied and fell off in a pile of goo so after all that I can't examine the epigyne. I suppose I should have put her in alcohol sooner but I didn't want to kill her and did want to see how long she'd live and she was so frail I didn't want to try to examine her alive. I did look at at a piece of it under a microscope and there were microscopic critters feeding off her. I tried briefly but didn't get a good image of the bugs, I couldn't bear the smell. For lack of having anything else on hand I had fed her an earthworm months ago, I think her health declined after that and wonder if it was contaminated with bugs and had something to do with her decline or if it was just old age.

Added two more images,
her epigynum is still partly obscured by hair. She's molted at least once, maybe twice (I forget) since last time and grown another 2mm. Looks just like an A. ferox though. Do you think it's OK to move it and the other similar young ones that are misplaced or would you prefer I keep waiting for the hair to wear off?

A. ferox
Nice! I think it's pretty safe to move this one to A. ferox, though I would be hesitant about moving juveniles.

PS. Been very busy the last month and haven't had time to contribute to BugGuide... hope to be back within a week or two.

This is the one ...
I mostly want to move:

It's a busy time of year in general, I imagine a lot of us haven't been as active the past few weeks. :)

I'm suspicious about its placement, but don't think we have enough to go on to move it to A. ferox.

Maybe not to species ...
it looks just like mine did though and the well thought out comments on it misled me into thinking mine belonged to the wrong family. I don't want that to happen to someone else.

It looks like we need to add these
as another pair of similar looking spiders in different families. I think we have confirmed spiders from both families that look almost identical. However, with most of these spiders I think if we study them close enough we may be able to find a field marking of some sort to separate them. But, working with juveniles can be maddening. =)

I don't know ....
my gut instinct is that the other one is very likely the same species as mine, the same genus at least and the more likely scenario. All the other Cybaeus we have look different to me but the one you linked to is more subtle. You're going to make me work aren't you? I have to find a local Cybaeus now to see how different they look and revisit this. :)

There might be some obvious clues in the description in SONA or some other reference, but I don't have time to look right now.

What do you guys think of Callobius? It has the dark center pattern in

Nevermind, the eyes aren't right. This spider has oval ALEs, I think they are round in Callobius.

I think ...
after looking at some European examples that Kyron may be right, it could be A. ferox ... she's just not presenting in a way that I'm used to. I couldn't find a clear shot of an epigynum to compare to though so I'm not sure if that's right. I could kick myself, I didn't take a ventral of my other typical looking A. ferox to compare to because I thought it was pretty common and someone with a better camera than me would have already done it.

A. ferox
yes, maybe so. The dark coloring in the center of the abdomen of your specimen might just be a pattern/color variation? Everything else does seem to match very well. We should probably check to see if there are other species from that genus found in your range. I have that paper, but I don't have time to look through it today.

I read that as carapace instead of abdomen.

Could be....
here's a back-lit example from a French site that brings it out:

I think that and some of the shading made me think the carapace was too tapered. I thought the PMEs were too big after looking at some of the ones in the Guide, but after looking at more I don't think so anymore. The color and pattern on the abdomen can vary quite a bit.

Epigynum images
There are some A. ferox epigynum images from the page you linked to about the carapace:
And diagrams here:

If you can get a shot, it probably doesn't need to be too clear, just enough to rule out other possibilities.

The epigynum is obscured (I don't know the name for the hood that's covering it), I don't know how I'd get a picture of it without hurting her. You're right though, I missed the ventral on that website - there's an example of it obscured there too.

The picture you linked to looks like it's of a juvenile. We should be able to see the epigynum at least partially, as here:

Maybe yours still has a molt to go? If she's an adult there should be something projecting, even if it's covered by hair.

She's an adult size, I'll keep watching her though. Maybe she'll molt again.

New images
I added some new images, she's roughly doubled in size.

Based on the comments on this one she might be Cybaeus silicis:

eyes, spinnerets, iridescence
I added some eyes and spinnerets. Another thing to note is the spider is slightly iridescent, at first I thought it might have been an issue with my camera or a weird reflection but after taking more pictures I'm sure it's not. I saw several others in the guide with the same iridescence:

When I see iridescence I always check out Cybaeidae.

I don't know if that's what it is, just throwing that tidbit out there. Here is what I copied from the similar spiders article: SONA says that Cybaeidae differs from other families by spinneret characters (3 longitudinally arranged pairs), ventral tibial macrosetae (numberous and conspicuous) and smaller size (1-14 mm). In my opinion Cybaeidae may appear to have longer legs in relation to its body than Amaurobiidae.

I see a little iridescence in Hahniidae too.

Moved from Spiders.

Maybe, but why can't I see the spinnerets? Usually on Coras they are visible from this angle.

Spinnerets added. I think they're small because she's immature.

There are some things which I'm not sure fit with Coras, but I don't know the genus too well. The spinnerets do look small and I can't tell whether or not the posterior pair has the long distal segments (I get the feeling the posterior ones are short and stubby). The chelicerae don't seem very robust. The PMEs in Coras are supposed to be smallest, but they look relatively equal here (hard to tell though). The legs don't look as spiny as I'm used to seeing in Coras, and I only see one mesal spine at the end of femur I. The carapace might be a bit short too?

If she's immature maybe these things will change, I don't know.

I guess I'll keep her for a while then.

Actually I just changed my mind about the spinnerets. They still look a bit small, but I think the posterior pair does at least have pointed distal segments. It'll be interesting to see how she develops.

young Coras?
Yes, please just keep us updated as she grows if you can. The pattern sure does look like a Coras sp.

More pictures.
I still have her, she's big and fat now. :)

A. ferox?
The pattern is starting to remind me of A. ferox?

I don't think...
she's an A. ferox, the shape and pattern of the carapace and eyes is subtly different. She's several mm larger than that A. ferox now. I was still thinking she might belong in Cybaeidae?

Hmm. Is she an adult yet? A ventral view that shows some epigynum detail might be able to rule out A. ferox at least.

Edit: This spider has a cribellum... I can't seem to find something that discusses whether any cybaeids have it. The ones I've found so far don't (e.g.,

Good catch ... I think she's an adult. I found a paper that mentioned Cybaeus cribelloides possibly having a small cribellum ... but after looking at European examples I'm starting to think you might be right it could be A. ferox. This one is over my head. :)

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