>> For there to be resistance there must be a genetic trait present in the >> current population that will allow the bee to survive when its beathing >> tubes are clogged with parasites. >It Ain't Necessarily So! A trait such are good grooming could tip the >balance in bee's favor. A very good point. My example was way too specific. My corrected point should be that the trait, whatever it may be, needs to already exist, or a fortunate mutation must occur. (A bee that grooms more could get the mite while it is questing for a new host).