Bob Harrison wrote

>  As i said in a previous post the large cell (man created)foundation is
the
>  cause of Varroa Jacobsoni to switch host from Apis Cerana to A. Melifera.
>  In 1985 "Encylopedia of Beekeeping" was printed and is edited by Roger
> Morse and Ted Hooper. The book convenced me in 1985 of the source of the
> problem.  Very little was known about Varroa then and all that was was put
in the
> book including a map on page 396 of worldwide varroa distribution.

I have been following this cell size debate with interest.  However, I
thought that there should be an update on the information above.  As we now
know Varroa jacobsoni does not reproduce on Apis mellifera and it is Varroa
destructor that is the pathogenic variety.  This is from the recent work by
Dr. Denis Anderson.

 Having heard Dr. Anderson talk on several occasions, he says that the
reason
why this is so is that there are triggers that the different Varroas need to
lay eggs.  The real Varroa jacobsoni does all the things that Varroa
destructor does except that it does not lay the eggs.  Varroa jacobsoni
enters the cell just before capping, it hids in the food at the bottom of
the cell and later emerges and positions itself on the same position on the
pupating larvae but does not go to the next phase of laying eggs.  It even
makes the same mark on the abdomen.

 So cell size is certainly not the point here as Varroa jacobsoni has the
opportunity to reproduce in the large cell that we provide for the bees.  I
have measured some that we produce here in Australia and the average cell
size for those I measured in between 5.4 and 5.7mm.

 The other interesting factor is that there is a link between the different
species of Varroa and different subspecies of Apis cerana.  Varroa jacobsoni
will not reproduce on the subspecies of cerana that Varroa destructor
reproduces on and vice versa.

 Dr. Anderson is continuing to work on the Varroa destructor problem and has
hinted that he has some idea what the triggers are.  It is hoped that he can
fulfill this research and bring relief to thousands of beekeepers world
wide.

 Trevor Weatherhead
AUSTRALIA