...natural experiment suggests that feral hives, with smaller cell sizes,
did succumb to Varroa infestation.

What about those rare occassions where a feral colony is found, and evidence
might suggest that it has been in continual existance for more than a couple
of years?  Might we beekeepers use these colonies in an attempt to determine
if they are, in fact, resistant to mite infestations.  Then, if so
determined, use them in an attempt to determine the causitive factors for
this resistance to mites?  I have several "beehavers" in the area whom I
hope to approach in an interest in determining just how "mite resistant"
their colonies are.  If the colonies "seem" to be mite resistant in some
way, I hope to encourage them to make splits next spring and buy several
splits from each.  Just looking for a way with some modicum of scientific
method.

Mike Stoops
1/2 way between Montgomery & Mobile, Alabama, USA