>
>
> >What was the adaptive behavior/selective pressure involved in varroa's
> jump from apis cerana to mellifera? A target of opportunity or some genetic
> change?
>

The mite can obviously evolve, as evidenced by populations that have
developed resistance to various miticides.

 As far as I can tell (guess), the Korea haplotype of varroa  was
apparently founded by a single female that responded to 4th-instar worker
pheromone to enter worker cells, as opposed to other haplotypes of varroa,
which avoid worker cells, apparently due to the self-sacrifice of worker
pupae that cue to a component of varroa saliva.  That mutant female appears
to be the foundress of the Korea haplotype that now infests *Apis mellifera*
 worldwide.

As far as further adaptation, I was conversing with Dr. Stephen Martin last
week.  It appears to both of us that the Korea haplotype has evolved very
little since then as far as adapting to *A. mellifera*  -- it's still far
better adapted to parasitizing *A. ceranae* drone brood.

There has been a study from South Africa that suggests that varroa there
may be evolving towards the parasitization of worker brood.  As I pointed
out in an article last year, if we made an effort to select for *A.
mellifera* worker larvae that committed self sacrifice when cued by mite
saliva, we could largely solve The Varroa Problem.

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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