10/25/2021: Getting spooky with communal cellar spiders

Social. Spiders. These are definitely not two words that usually go together. There are only two examples that come to mind, those being communal housing success of Monocentropus balfouri siblings into adulthood (though not being a T guy in particular I don’t know how successful this tends to be long-term) and the communal cobweb spider Anelosimus studiosus that I have known at least 4 people lusting after on multiple different Florida trips. Neither of these really suit my… style per say. However, on a particularly animus road in Animas, New Mexico I’ve finally been caught in the social spider love web.

Flipping boulders for Arenivaga generally turns up plenty of other goodies, and under a large volcanic boulder with a generous tunnel excavated beneath it from one side to the other was a gigantic web network. Unlike every other boulder flipped, there was no solo spider or scattered individuals; this was one giant commune of Pholcids. Cellar spiders are generally pretty tolerant of each other where found in houses, basements, and buildings, and it’s not unusual to see 2-4 with webs hung very close or touching. What made these Pholcids different was the sheer density of spiders and age distribution; every size from egg mass to adult males was present, perhaps a thousand individuals within a 2 square foot space, all in the same web cluster, some pretty much on top of each other.

This was the only group of these spiders we found on the whole stretch of road. It seems likely to me desert conditions would be ideal for forcing group behavior adaptations; sharing a web means being able to capture larger prey, not have to wander to find mates, protection from desiccation, and a slew of other benefits for species that already have behavioral pre-adaptations for group living.

With Will and Ben’s helped I captured as many as I could to take back to culture (all the while freaking out about how delicate they were; trying to fit as many spiders as you can into a deli cup while worrying about them trampling each other is quite the experience), and today the colony seems to be doing well. The set-up is an inverted critter keeper to make emptying out waste and feeding easier, and a small crop of babies has popped up and appears to be doing alright. I’m debating expanding the colony into a larger enclosure, but I think there may be too many things that could go wrong with scaling them up until I have a few more generations under my belt.

Pholcid identification isn’t the easiest thing but I think they are a Physocyclus species. Maybe when I have surplus of sexually matures I can send one off for proper identification somewhere. As distinctive as communal behavior is it’s also likely it’s poorly described as is the life history for most non domestic Pholcids.

-Kyle