Sunday, August 23, 2009

Night spider.

Last night against the afterglow I saw a spider hanging motionless from the tip of a branch. Its legs were spread, the way a crab spider lurks in a flower. Did it have a web? I don't think so; it was just hanging there. I don't know if spiders ever catch anything this way. It wouldn't seem particularly efficient or easy.


The flash of the camera disturbed it, but it didn't retreat. It was probably blinking at eight purple post-flash globs, wondering what hit it. Sorry, spider. I checked the spot this morning--no web. I'll check again tonight, perhaps capture the beast to identify it.

7 comments:

Tim said...

Many spiders use this technique to dangle to a more breezy portion of air (further from the branch or tree) and catch a gust of wind to carry a bit of invisible silk in the wind. The outstretched legs are to orient their body to face the wind (and possibly to detect the right moment to release the silk).

Hugh said...

Tim, so this may be a sort of air-trolling? It makes more sense than anything I came up with. Do you know if there's a name for this behaviour in spider literature?

Spidey isn't there tonight. Could it be a thomisiid?

Tim said...

In spiderlings, the behaviour is called "ballooning". After their first or second molt, the spiders are too massive to be physically lifted by a gust of wind, but they'll still use the same strategy with silk to travel to distant lands (but usually just waiting for the silk to snag on something at the other end before walking across it). Whether this is still called balooning, I do not know.

Ok, did some additional research: "Bridging" seems to be the term used most often, as referenced here: http://www.americanarachnology.org/JoA_free/JoA_v23_n3/%20JoA_v23_p202.pdf

Tim said...

As for the species ID, I don't really know, but I do not think it's a crab spider. Crab spiders tend to have a longer second leg than the first leg, where your photo has the first longer than the second. If I were to guess from pictures, I'd guess it's an orb weaver Zygiella atrica, though the range of the Zygiella x-notata makes it more likely to be found here. (http://en.wikipedia.org/wiki/Zygiella_x-notata).

Their webs are probably the most common in rural Richmond, though not as significant in size than the araneus diadematus species. They are, themselves, seldomly seen as they hide out in their retreat during the day, whereas the araneus diadematus hides out only when it gets larger. Additionally, the construction of the web will typically leave out a triangular section in the same direction where the retreat line runs to the retreat.

Tim said...

In my latest comment, I meant to say "in urban Richmond", not "in rural Richmond".

Hugh said...

Thanks for the research, Tim. I think you're right. It looks a lot like a Zygiella.

spinyurchin said...

Yes, thanks Tim!