> A.cerana is much smaller than A. mellifera which means that
> A.cerana's cells must be much smaller than A. mellifera's. In
> spite of that varroa can live in cerana's cells...

In all this discussion of smaller cell size I have wondered if it the RATIO
of extra to occupied space (E:O) that may be the influence.  Apis cerena
certainly has a smaller cell size, but it could perhaps have the same E:O as
does the larger Apis meliffera.

As cell size decreases, assuming the larva/pupa size remains the same, then
the E:O also decreases.  Perhaps it is the reduced E:O that negatively
impacts Varroa.  Perhaps the Varroa simply has not enough room to move to be
as successful as it would be in a more spacious cell.

Aaron Morris - thinking don't fence me in!