Argiope trifasciata shaking its web in response to being approached.
This past weekend I made a trip to the White River Hills region in extreme southwestern Missouri. My goal was to find additional localities of the prairie tiger beetle (Cicindelidia obsoleta vulturina), which inhabits dolomite glades in the area and is disjunct from the main distribution in Texas and Oklahoma. As I was checking a particularly large glade complex in Roaring River State Park, I came upon this banded garden spider (Argiope trifasciata) that had spun its web across the span of branches from a gum bumelia tree (Sideroxylon lanuginosum). As I approached the spider the web began moving back and forth quite vigorously, and it occurred to me that there was not nearly enough wind for the web to be shaking to such degree. I stood still, and eventually the shaking stopped and the web became still again. To test whether it was really the spider shaking the web intentionally, I raised my net to one side and drew it closer to the spider, and once again the web began shaking back and forth just as vigorously as before. I watched the spider closely as the web shook, and I could see that the spider was actually flexing its two front pairs of legs back and forth to cause the shaking. It was clear at this point that the spider was doing this in response to my approach, probably as a defensive reaction to a perceived threat.
I suppose I have seen this behavior before but always assumed the web was just shaking in the breeze. Not until this time, with no wind to speak of and the web shaking quite rapidly, did it become clear to me that this was actually an intentional behavior exhibited by the spider. Eisner (2005) also notes this behavior, stating that Argiope spiders often engage…
…in a bobbing action, whereby through a quick flexion of its legs it sets the web into vibration, making itself a blurred target that is hard to grasp.
The photos used to make this animated gif were not easy to get. The spider was situated in a rather high and awkward-to-reach spot, and the iPhone had difficulty focusing on the spider while it was in motion. I overcame these problems by setting myself in a stable position, holding the iPhone in place, zooming the screen slightly (about 33%) and locking focus on the spider while it was still, and then asking my field buddy (Steve Penn) to approach the spider to trigger shaking. Once it began shaking it was a matter of holding down the shutter while keeping myself and the camera still long enough for a sufficient burst of photos (eight photos were used in this gif).
REFERENCE:
Eisner, T. 2005. For the Love of Insects. Harvard University Press, Cambridge, Massachusetts, 448 pp. [Google Books].
© Ted C. MacRae 2014
Beetles In The Bush 
Ted, here is one garden spider from friend Bob Kipfer blog worth a look…
http://springfieldmn.blogspot.com/2014/09/hummingbird-predator.html
My Best,
George Deatz
That’s pretty amazing!
I believe the spider in Bob’s blog is A. aurantia rather than A. trifasciata. Note the alternate black/yellow banding on the legs of the spider in my post, versus the solid black outer leg segments in the spider on Bob’s blog.
Hi Ted, quite remarkable behaviour, that the spider builds the web and uses it to extend its gestures. I am enjoying reading your blog, I have no credentials in entomology beyond curiosity but I have thought about trying to identify the spiders I find in my home. Can you suggest any resources for doing this? I live in the UK.
Hi Joshua – thanks for reading. You might try the British Arachnological Society (http://wiki.britishspiders.org.uk) – I’ll bet they can point you to lots of good resources for spider identification.
Thanks for that, Ted.
Nice gif. I have Argiope bruennichi in my orchard in France. I’ve never noticed this behaviour, but like you probably mistook it for the wind. I’ll have to observe more closely now. I have the spider in large numbers and recently paid the guy who mowed the orchard in kidnapped spiders. He lives in the next valley and his colony has died out. We took the opportunity to do a little assisted migration.
Awesome that you are promoting use of the spiders for biocontrol in your orchards. Bravo!
This is a very interesting display of behaviour, I would be interested to know how many other spider species exhibit this behaviour.
I am a huge spider fan, especially tarantula’s! I used to keep many tarantula’s in the UK before moving to China. I am in fact generally a bit of an insect fan in general, so i am very happy that i chanced across your blog, i shall be following it closely! I really enjoy all the behavioural aspects of animals. Having done animal behaviour at university, it is something that is particularly close to my heart.
James
themanabroad.wordpress.com
Hi James – welcome to BitB, and thanks for the kind remarks. There are apparently some other groups of spiders that also show this behavior, based on comments to the link that was placed on my Twitter feed (I don’t know why people prefer leaving comments at outreach links on other platforms rather than here with the post itself – those other comments quickly become orphaned and basically ‘lost’). Really I’m just having fun using these animated gifs to demonstrate behaviors that can’t be demonstrated in still photos (I know videos would work even better, but I don’t have equipment to do macro video).
What equipment do you use?
The photos for the animated gif in this post were taken with my iPhone – cool, huh?
For my “real” insect photographs I have a Canon 50D with 100-mm and 65-mm macro lenses and a lens-mounted twin flash.
Awesome, i remember seeing you mention using the iphone in the blog. I want a macro lens. the 100mm is L glass right?
No, I don’t have the L-series version of that lens.
Are the argiope trifasciata poisonous?
All spiders are venomous (poisonous refers to something dangerous to eat), but only a few have bites that cause more than a small welt and none are aggressive towards people that don’t try to handle them.