A Social Spider In North America

 
A highlight of my recent excursion to the University of Texas at Austin was learning about some little spiders, Anelosimus studiosus, that spin messy webs in the undergrowth. Remarkably, these spiders are communal. Most arachnids are solitary predators, but Anelosimus studiosus lives and hunts in shared webs. 

These social tendencies render Anelosimus exactly the sort of spider that might lure an ant biologist. And of course, that is how I happened to hear of them. UT’s famous ant-fungus lab, the one headed by Ulrich Mueller, has a student, Emma Dietrich, working on the spiders. Emma was kind enough to collect a few webs from around campus for me to photograph.

 
Anelosimus studiosus is typically subsocial- meaning that young spiders remain with their mother in the web but disperse at maturity- but populations in colder parts of the range are properly social, with multiple breeding adults sharing webs.

I had always thought of spider sociality as a tropical phenomenon. I observed another species of Anelosimus, for example, on my last trip to Ecuador. But social spiders right here in the temperate zones of the United States? Fantastic!

 

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source: Furey, RE. 1998. Two cooperatively social populations of the theridiid spider Anelosimus studiosus in a temperate region. Animal Behaviour 55, no. 3 (1998): 727-735.