>> 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).