Wasps generally are predators, not plant eaters, so it might be looking for mealies or other pests to much on.

A couple days ago I found a piece of yellow jacket nest on the ground before I took a pic of my Adenium:).

Wasps stripped the surface from my dark blue painted pergola uprights last year to build a beautiful football size nest amongst my red currant bushes. Guess what, the nest was a lovely shade of blue/grey! They start from the top and work down as Bunkfree showed, I could actually hear them rasping my beautiful paint away! Amazing really, and the structure they build is truly a work of art, humans can build, but so can the wasps!

Whoa, I had no idea that they would ever do that! That's an incredible amount of damage.

Do you think it could be a Sand Wasp or Square-headed wasp? http://www.toronto-wildlife.com/Insects/Bees_Wasps/Wasps/wasps.html

In my area we have problems with carpenter bees. You can very clearly hear them, in the evening, rasping inside the wood.

Thank you, everybody! Yes, I think they use the felt, probably for nests then. The plants are free of pests, I would have noticed something lurking under the smooth whiteness. There is a pot of furry Kalanchoes right next to this one. I saw one wasp go to it, do something with its legs for a moment, and leave. That stuff does not come off easily ;-). I also found another wasp gathering the felt, I am not sure it was the same kind.

Interesting link, Kevin. It could very well be either of those. I will try to have a better look next time. That big head of the Square-headed wasp is quite noticeable. I will leave the plant for the time being, it is kind of interesting to see, but then it goes. I friend thought it looked interesting. I don't...

I also have carpenter bees. I will have to see what they are up to, they fly to the foundation of the house. I am never downstairs on that side of the house in the evening, so I don't hear a thing, but I found one dying one inside just yesterday.

Those wasps really are wool gatherers! On Sunday I saw one go up to a previously 'harvested' pile of fuzz, gather it into a ball with mouth and forelegs, compact the ball against its chest, hold it with the forelegs and fly off. It was wonderful to watch! Miracle of creation.

I have a Golden Goddess bamboo that I noticed wasps all over, they strip fibers off the bamboo to make nests too. I had no idea they would strip paint / fencing or fuzzy succulents!