Steve Noble wrote:

> You would have to assume that if such a
>mechanism does exist it would have to have been the result of evolution
>over long periods of time in response to stresses that have also existed
>for long periods of time. 

Precisely. Dr. Kralj states that it wouldn't be a direct response to varroa
since European bees haven't been associated with them long enough to 
produce a specific response to that pest. Rather, it would a generalized
response to parasites and/or pathogens in general and if it is from the
distant evolutionary past then it may be shared with other species of Apis. 

Most of Apis is tropical and a response such as the depletion of the large
part of the adult population would not necessarily kill the colony, if the
queen and a few thousand workers remained. The effect is similar but
different from absconding, which is common in tropical Apis but fairly
unusual in Apis mellifera. Personally, I have seen colonies abscond due to
ant attacks.

pb

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