Behavioral Mimicry in the Golden Garden Spider

I witnessed a pretty awesome display today by my friendly neighborhood Golden Garden Spider (Argiope aurantia), that I had never before seen. In fact, I had no idea that spiders would make such defensive displays.

As I approached her web, I noticed the web start to vibrate back and forth in quite an exaggerated fashion. So I ran and grabbed my camera. When I got back out she had stopped, but she started back up immediately as I got close.

Note - my hand is actually about 6 inches from the web. Also, my hand produced no wind (you can see this clearly toward the end of the video - the last ten seconds are by far the best).

Considering the bright yellow and black markings, my nearest guess is that she was mimicking the movement of a carpenter bee or some other poisonous hymenopteran (we have lots of carpenter bees). It seems clear that it was her way of saying "get the fuck away from me! I'm dangerous". Of course, it may be that it's not mimicry at all, but to me it looks very similar to the movement of the carpenter bees against that very same wood as they bob forward and backward.

For another cool picture of an Argiope, see my previous post (which also has some cool black widows from my house).