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Photo#395964
ID for a large orb-weaver? - Araneus andrewsi

ID for a large orb-weaver? - Araneus andrewsi
Claremont, Los Angeles County, California, USA
May 14, 2010
Size: Body approx. 2.5 cm?
This large spider spun an orb web on the top of the gate to the Claremont Colleges' Robert J. Bernard Biological Field Station and has been out on the web nearly every night for the past several weeks, but it hides during the day. My colleague Tad Beckman used a flash to take this photo of it at about 8 pm.

Images of this individual: tag all
ID for a large orb-weaver? - Araneus andrewsi ID for a large orb-weaver? - Araneus andrewsi ID for a large orb-weaver? - Araneus andrewsi ID for a large orb-weaver? - Araneus andrewsi ID for a large orb-weaver? - Araneus andrewsi - female ID for a large orb-weaver? - Araneus andrewsi - female

Moved
Moved from Spiders.

As with most spider identifications, determining species is somewhat of a guessing game without dissection of the specimen's genitalia. However, it seems that several sources have now agreed that this is very likely A. andrewsi and that measure of consensus is often good enough for BugGuide's purposes. I'm moving these images to the species page, with the implicit understanding that it is plausible that this might in fact be another similar-looking species. If anyone disagrees with this decision, please do let me know! :-)

One possibility is Araneus andrewsi
Levi, 1973, pg 481, but we're still looking.
Can you get a ventral image?

 
Perhaps A. gemmoides?? Wh
Perhaps A. gemmoides??

Why not collect her, cool her down in the fridge a bit and take a look under the microscope?

-K

 
Great suggestion, but...
Thanks, Kevin, for your suggestion. I'll see if I can figure out a way to collect her, but it's a little complicated. First, the spider is about 9 or 10 ft up in the air, so I'd need to haul a ladder over to the field station. (The photos were taken with a long-focal length zoom lens.) Second, I'm not quite sure how to collect a big spider like this (my sole collecting experience is catching spiders in the house to take outside). And third, although I do have a microscope, I don't have a clue as to what I would be looking for. I'll e-mail various folks I know in the Claremont area to see if I can turn up anyone who could help collect and has the knowledge to do the ID.

 
Don't do anything dangerous (
Don't do anything dangerous (thinking not of the spider, but of overhead wires, moving gates, ladders, etc.)!

Collecting orb weavers is generally quite easy. You need to position a container directly below the spider, taking care not to disturb any attachment lines of the web. Then prod or "disturb" her from above and she will most likely drop straight down. Note that she may trail a safety line, so if you move the container too rapidly she may lift back out.

Note also that if you've never done something like this before, you might not want to try it for the first time at the top of a ladder! BTW, someone who is very familiar with your local spiders might recognize it from your photo, especially if you can add a ventral view.

-K

 
CA Araneus
I would lean more toward andrewsi, but since it seems like the photographer may have access to a local expert, it would be really nice to have a definite ID.

 
Will try later for ventral image
Thanks, John and Jane! I've posted a couple of other images, but we don't have a ventral image. Tad needed to be on the other side of the gate, and he didn't have the combination with him. I'll see if he can go back (with the combo!) and try to get a photo of the ventral side.

 
Ventral image!
Well, we now have a ventral image of the spider. I hope it shows enough detail to be useful. The poor spider has had a hard view days. Last Friday night some vandals threw sticks at the web (or the spider) and pretty much wrecked the orb web. Saturday and Sunday she built a new orb web to the side of the gate. The new web is smaller, but at least it's attached to something stationary. And fortunately for us, it's a bit lower down, so it only took a short ladder and moderate zoom to get the ventral shot. :-) I've also added new dorsal and side views -- they're a bit sharper than the previous photos.

 
The long scape and the propor
The long scape and the proportions of the epigynum that one can see certainly speak for A. andrewsi. Not sure, though, what other possibilities there might be (none that occur to me just now).

-Kevin

 
A. andrewsi
I agree. Good job getting the ventral view.

 
Another opinion
I e-mailed the Spider Survey team at the Natural History Museum of Los Angels County (http://www.phorid.net/spiders/spiders_index.htm). Jan Kampf replied that:

"The spider might be Araneus andrewsi. It is not possible to be positive with only a photo. A. andrewsi has two large humps on the anterior abdomen and a folium like this, but is usually very dark. It isn't possible to tell if the spider is as light as it looks or if it is dark. It is not gemma or gemmoides."

I think the color in the photos is reasonably close to the actual color, but the flash does tend to wash colors out. In any event, it looks like opinion is converging on Araneus andrewsi. Thank you, everyone!

 
Kempf. -Kevin
Kempf.

-Kevin

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