Exponential Orbweaver

A gregarious orbweaver in Argentina.

Another arachnid post.  These spiders were one of the most striking arthropods we encountered in Argentina.  The females of these colorful spiders are nearly palm sized.  Communities of these gregarious or sub-social spiders form their webs in large groups, thus filling a small area with many, many huge spiders.  This lead to some interesting encounters.  Myrmecologists scouring the ground for fire ant nests aren’t always particularly aware of, say, what might be going on with spiderwebs in the trees they’re walking through.

An aggregation of gregarious orbweavers in Argentina

It is very disconcerting for the spider-wary to accidentally stumble into one of these clusters of giant spiders.  Luckily, I did not find them to be particularly aggressive.  The webs are sturdy, however, and capable of straining fairly large flying prey from the air.  We even saw a bird become trapped in one of these webs for several minutes before it beat its way free.

A bird caught in the web of gregarious orbweavers (photo by Dr. Shawn Wilder).

In truth, I haven’t been able to find out much about these spiders.  Does anybody know of any good references?