Questions about Pholcidae sp.

[LinotheleLover]

At my job, there are literally thousands of cellar spiders. The amount of fly corpses discarded from their webs is even more numerous, its honestly extremely impressive how well adapted this family is to urbanization. This got me curious, are pholcidae truly communal/gregarious? I've attached a picture of two large specimens very close in proximity, so I'd assume yes but I've never thought about it. Secondly, is the other picture a mother holding an egg sac? Its definitely not a prey item. And finally, if I want to keep one in captivity, should I put it in an enclosure or would putting it in a corner of my house and periodically feeding be more ideal for it?

 

[The Snark]

are pholcidae truly communal/gregarious?

Yes.
Pholcids. An enigma in the spider world.
If your pholcids are typical and you look closely at the webs of your spiders there on the job you will note they randomly interconnect and it can be difficult to find any clear boundaries between the webs. They usually have their own preferred trapping areas but males will often host several females that cross the boundaries or even live in the male web.
You may note the dead prey about might include other species of spiders but rarely if ever their fellow pholcids.
Notice the differences in sizes of the pholcids present. Numerous generations are usually found in those interconnecting - communal webs. The younger smaller ones will make outliers so they have a better chance of getting fed, but still their webs often interconnect here and there, using the adults guy lines for anchor points.

During your observations keep in mind the unique capabilities of the pholcids. Their webs have no sticky threads. Thus the webs themselves aren't a hazard to other pholcids. Their prey capture method is purely combative, wrangling whatever enters the web, Some deliver multiple nips to subdue the prey while others rely entirely on tying up the victim. This may play a part in their allowing other pholcids into their webs; They are extremely adept at wrangling their prey and just about any alien - non pholcid spider normally escapes or is subdued. Pholcids seldom if ever lose these fights. A combination of those long legs and their maze of webbing. This is significant in that the web maze is purely pholcid oriented. How this works I have no clue after hours of observation comparing pholcid webs to other cobwebs. But one result is pholcids aren't inhibited or have any difficulty negotiating another pholcids web -seemingly without fear of becoming prey.
One would think other species of spiders, say latrodectus, steatoda, even salticids, all of which have much greater power in their legs due to mechanical advantage would be able to defeat a pholcid but this is simply not the case.

And a something to ponder. Look at the legs of the pholcids. Covered with evenly spaced spines. These spines resemble the combed feet of web based spiders. So it appears, guessing here, that they can maneuver and manipulate the webs and their walking in the webs with any part of any leg. This would help explain why they are such capable combatants.

Another oddity is they never ingest or cut and discard their webbing. Thus pholcid webs will never get smaller and the maze always becomes more and more complex.