> I am still convinced as was Brother Adam that resistance to tracheal mites >can be selected for. A 20% loss is acceptable to me and is easily recovered >from by pulling a few frames here and there from the survivors which also >helps with swarm control. 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. IF the trait is present AND the trait does not carry with it additional negative traits (such as abscounding) then and only then can a breeding program eliminate other controls. One must also remember that we are only talking about tolerance, unless the trait found kills the mite. You also have to consider that when breeding a better Bee, you may at the very same time be breeding a better mite. Evolution does not look ahead. If a parasite mutates and in two generations kills the entire population of hosts that is just the way it is. Multi-species extinction seems to have been around a long time before beekeepers.