>> For any claim in tolerance, I would like to see evidence that there are
no mites in the hive.
 
>Consider Apis cerana. They have varroa living in their hive and yet
>survive.  The mite has not been wiped out there. I think this is the
>best we can ever hope for with Apis m.
 
Varroa is the natural pathogen for a. cerana.  This type of bee is common
through out Asia including Sri Lanka.  A beekeeper from Sri Lanka once
explained to me how a. cerana has learn to tolerate the mites.
 
As I understand it, Varroa is not a serious problem for these bees because
they have learnt to tolerate them by grooming.
 
The mites like to ride piggy back on the adult bees.  This is how they
spread themselves around.  The bees don't particularly like this and can
wipe them off.  Their legs have evolved so that every part of the body can
be reached by at least one leg.  When adults feel a mite jump aboard for a
ride, they simply brush it off.
 
Presumably this happens outside the colony before the mite has hitched its
ride back to the colony.  Thus the mite population does not have the
opportunity build up within the colony.
 
As a fail safe solution, a. cerana will abscond from the old hive when
things get tough.
If the mites get to heavy to handle, all the adults leave and leave behind
the heavily infested brood.
 
Theocratically, Apis m. might also evolve to groom the mites off.  Just give
them a few million years and they'll be alright.
Regards
 
Chris Allen