>if for some reason hosts do not become more scarce, then this automatic natural selection of milder variants of the pathogen will not occur. 

Succinctly put and thanks Pete. The argument that it is not in the interest of a parasite to kill its host and thus we should expect a less virulent form of varroa is unrealistic for just the reason sited. For the same reason we do not see less virulent malaria or cholera. If hosts are plentiful the incentive for the pathogen is to keep doing what is working.

I believe that the reason we are seeing some colonies survive mite infestation is all about those particular bees ability to control varroa and not varroa becoming less virulent. I also believe that the change in behavior would occur in evolutionary time on both sides and not the 25 +/- years varroa has been with us here. We are actively trying to push evolution on the bee side (with some limited success) but the mites are on their own and unfortunately we supply plenty of targets. I have long thought that we would do well to spend more research on exploring mite biology and vulnerability and pushing evolution to make them less able to reproduce on A. mellifera.

I am aware of Tom Seeley's work with feral colonies but believe that so far when those bees are brought under management they do not bring their mite tolerance with them. Am I wrong about that?

Paul Hosticka
Dayton WA

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