I had to report that I found where all the dust that is not going through my air filter is going.  A dustbunny, more like a giant German dustrabbit, has been living on our income in a hard to reach corner under the bed.  When I found it, my heart almost failed: you know how sometimes when you look at a very big bug you have the sense that it is looking back at you . . . what if it jumped on me?  I had a hard time nerving myself to go after it, even at the relatively safe distance of my dustmop handle.  Fortunately all the character building cartoons I’ve watched came to my aid.
I am happy to report that it has been exterminated.