from a 1993 article in Bee World "Science Roundup: the IBRA Symposium
'Living with Varroa"

        Honeybee colonies vary in susceptibility to varroa, holding
out the hope for the breeding of colonies with greater *tolerance* of
varroa.
        specific characters ... implicated in this reduced susceptibility...
        * ability to bite and groom mites from themselves and nestmates
        * ability to preferentially remove sealed brood infested with
mites (hygienic behavior)
        * shorter duration of the sealed brood stage...



from a 1994 article "Response of Hygienic Honey Bees to Varroa jacobsoni Mites"

        it is important to determine if honey bees have any natural,
heritable defense mechanisms against the mite that may be readily
incorporated into breeding programs...
        Hygienic behavior is considered the primary mechanism of
*resistance* to at least two diseases of larval and pupal honey
bees...
        Lines of hygienic and non-hygienic colonies were bred and
tested for their ability to remove pupae infested with Varroa mites.
        In 1994, the experiments included four hygienic and three
non-hygienic colonies; and in 1995, seven hygienic and four
non-hygienic colonies.
        Further tests will determine if the variation between years
was due to genetic or environmental causes.

        6 years later this same author is says "despite some claims
to the contrary, there are no beekeepers or researchers who have
successfully bred a line of bees that is varroa resistant".


        A thorough reading of the literature will show that the terms
varroa resistance and tolerance are used to refer to the same
assortment of behaviors which honeybees use to try to rid themselves
of varroa infestations.
        The question is not whether these behaviors are present nor
what they should be called. It is whether they form heritable
characteristic(s) that can be bred into bees and propagated by the
distribution of queen bees. It appears that there isn't agreement on
this key point.