hi tom
       YES,YES, YES. a nice appraisal. but the mite does not make a
decission to change their biology to combat a our efforts in thier
population control.  put simply when we use any control we kill most of the
mites suseptable to the control, there is always a genetic variation in  a
population and amongst that variation there will be a small number able to
survive that breed more survivors for that control method. so if you cull
drone comb your selecting for mites that breed in worker brood,if you use
apistan your selecting for apistan resistant mites ect ect ect any
resistance to any treatment depends on breeding generations and the number
treatments used and the variation between unrelated treatment in use. so the
only answer is to find a bee that the varroa doesnt kill when it reproduces
and that can pysically cope with the change in the virus and disease flora
that hapens when varroa arrives, that too is selection and takes time.
     kill enough bees and the resistant ones survive and breed more
survivours.
                                                   apistan resistant
varroa<>vorroa resistant bees