it is also possible that the mites came in on the bedding. If you bought the bedding from a store that has mite infested snakes, they may have somehow hitched a ride from the store to your home on a nice cushion of aspen. I'd say to dump the aspen, treat the enclosure with the Provent-A-Mite (really easy to follow directions on the can) and put him on paper towels or newspaper until the mites are gone. After that, you can go back to aspen, but you'll want to bake it first at the very least...