>DW>Why is it that the direct ancestors of insects found in resin 42 milion
>  >years old, will today die out in large numbers from the attack of a Varroa
>  >mite of equal pedigree. Surely in all that time similar threats have been
>  >dealt with successfully?
 
Varroa was not found on Apis Mellifera 42,000,000 years ago or even 100
years ago.
 
Varroa is a natural pathogen of Apis Cerana (AKA the Asian Honey Bee).  This
bee is a completely different species.  The adults are smaller than a.
mellifera and the colonies are also smaller (never big enough to fill more
than 2 small boxes).  The honey yield from this species is also small.
 
Among other things this species HAS evolved to tolerate Varroa.  The bees
simply brush them off with a highly developed grooming technique.  For this
species Varroa is just a minor nuisance.
 
Problems for modern beekeepers began about 40 years ago.  At that time,
beekeepers in some parts of Asia tried to use a. mellifera in instead of a.
cerana.  They hoped to get a better yield of honey from a. mellifera.  It
appears that varroa jumped species at this point from a. cerana to a.
mellifera.  As a. mellifera had never been exposed to varroa before, they
have no effective defense and suffer badly for it.
 
It is likely that no one was aware of the problem at the time and so it was
allowed to spread unchecked through out Asia and Europe.  In addition, some
cretins kindly shipped it over the water to the UK and mainland America
(North & South?).  I believe it has not yet arrived in Africa.
 
I know it has not reached Australia, New Zealand or Hawaii.  Each of these 3
places are anxious to keep it out which is why they get nervous when other
people try too import bees.
Regards
 
Chris Allen