> Resistance to Varroa in honeybees is broadly described as the long-term survival of bee colonies without human treatment in a given habitat. In this, the term comprises more detailed definitions of resistance (the host’s ability to limit parasite burden) and tolerance (the host’s ability to limit the harm caused) used for individual animals and the ability to cope with various other environmental factors at the colony level. This became particularly evident when resistant honeybees were introduced into a foreign environment. There, their ability to overcome Varroa could no longer be observed. — Scientific Reports volume 13, Article number: 22484 (2023)

> Although many local sub-species exist, A. mellifera remains a single species and environmental conditions within the colony (i.e. those that Varroa are subject to) remain remarkably constant irrespective of location, which has aided its semi-domestication and global distribution. Natural bee-driven resistance to Varroa is a sustainable, long-term solution, prevents the constant usage of acaricides, will not weaken bees to any other maladies should they arise and may provide an example of parallel evolution with the same three traits arising in populations in several different continents. — Proc. R. Soc. B 288: 20211375. https://doi.org/10.1098/rspb.2021.1375

Comments: 
I find it interesting that these two statements seem to be at opposite ends of the spectrum where the first points to very specific environmentally tethered effects whereas the other seems to decouple behavior from the environment, pointing to the commonality of the in-hive environment where varroa mites actually live. 

Separately, I question whether resistant traits which may occur naturally in unmanaged populations can be scaled up to a conventional beekeeping setting where the colonies are in apiaries (often large ones) and the colonies are managed to have maximum populations for honey production. If varroa resistance depends on adaptation to local environmental factors, or to small non-managed colonies, it may not scale up to real-world beekeeping. 

Personally, I have noticed that varroa buildup seems to be greatest in the largest colonies during a good honey flow. This could be a result of several things such as: the workforce is diverted to honey production and away from monitoring the brood; or the conditions are simply much more favorable to mite proliferation in a very large colony. 

I would wager that very large colonies are not the norm in a lot of scenarios, such as bees that are managed to sell bees (nucs, packages, etc), or pollination where a lot of average sized colonies are best, or in a situation of little or no management, which at the very least does not lead to very large colonies and at worst — promotes swarming and population depletion. Swarming may be a great varroa control method, but it isn't good for honey production.

PLB

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