> >Why would one believe
> that bees from hives with a higher varroa population would be more
> likely to drift to those with smaller?

Actually, we talked about this before. Any sort of damage to the bees neurological system (pesticides, viruses, CO2) is likely to cause "mental" impairment. Light impairment could affect their ability to navigate, or remember the correct location of the hive. Bees are known to fly into the nearest hive they can find, at times. Severe impairment might cause them to simply fly off and not come back. 

Investigation reveals that some parasites even induce behaviors that cause distribution to new locations or new hosts. People make a lot of the notion that a parasite shouldn't kill its host. Another alternative is to get off the infected host (colony) and onto another. This may be a strategy that has evolved in the mite/bee relationship. As the colony is in its later stages of collapse, mite infestation could cause the bees to drift into other healthy hives. 

Getting back to the studies, however, what has been looked at is the reproduction of mites inside the cells. Regardless of drifting and apiary effects, a mechanism that reduces reproduction in the cells (small cells, varroa sensitive hygiene, etc) should be quantifiable, irrespective of the external reinfestation rate.

PLB

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