I'm pretty sure this is frass. I've suspected wood eating pests live in this building due to holes,  excess dust around wooden moldings, windowsills,  as well as entry holes in the wood. Even some strange holes appear out of nowhere in the plaster walls, in nonsense areas that nobody in their right mind would choose. Like below power outlets, just above the floor molding? Who would make a hole there,  other than a bug? Also I went around and filled all the wall holes,  and holes around the window in here before. I didn't create new holes since, I bought damage free 3M hanging materials instead,  just so I wouldnt need to make another hole in the wall. Other reasons i think there's wood eating bugs here,  is because the floors get these indented spots with hard white stuff in them, that won't come out, they're quite small,  but i periodically find another,  and another. Some parts of the floor even look chewed on the surface. There's alot of chewed looking wood around the windows, with paint chipping off frequently, though I'm not doing anything to induce the mechanics of paint chipping & dislodging from the surface. In the heavy amounts of dark dust that falls on the molding crevices below my windows,  are many black dots that could be bug poop. When i began noticing this activity years ago,  i warned the landlords only sent a PCO that said he only knows how to ID biting bugs??? I found that odd, don't they get trained to look for all kinds of bugs?  I only reported it,  because i was worried the eaters would eventually find my wooden furniture. Needless to say,  I'm now finding white indentations in my headboard. I think I may be allergic to whatever it is, as I'm itching often,especially after I dust the headboard, canopy & box the mattress fits inside of.  When I wipe it with wood cleaner, i find small black particles all over my hands after,  and it itches. My hands get red & puffy then. It seems a direct reaction.  I have read that people can be allergic to bug poop. I've even been getting bitten sometimes on my bed.. i just need to know what I'm dealing with.  This is the first time I've found this much of a pile of it at once, so it seems the issue is becoming worse.   :( 

also even plastic items are being chewed up by something here, but I think that's likely a different post. Unless there's a bug that eats anything it comes into contact with, lol.  Please advise....  Thanks in advance!