Thank you for posting this! I've been squashing them in the sun, vacuuming them and trapping them in those precarious top bar oil traps (which do work if you use enough of 'em). I so can't wait to try this. While not traumatized at the site of these buggers, I do take extreme joy in seeing them trapped and killed, I must admit.
Apparently the felt backing doesn't cause any problem for the bees themselves, or is separating the felt from the bees a requirement?