Interesting that no self-cleaning (or mate-cleaning) behavior has emerged. May be, given the bees vision, the attached mite isn't distinguishable from the rest of the bee?
Mite reproduction is hard to inhibit for both the bees and beekeepers. Female mites sneak into brood cells (cells used for bee reproduction) before the cells are capped and hide under the developing bee young. Once the cell is capped, the bees outside are unaware of what's happening within the cell. The mites lay their eggs within the capped cell, the eggs hatch, mate and emerge along with a diminished bee. This means Varroa treatments (such as oxalic acid vapour) only work if there are no capped brood, which only occurs at certain times during the year.
On the topic of vision it's worth pointing out that bees spend the majority of their time within the hive where it's completely dark. They only go out to forage late in their short lives. Their lifespans increase for winter, and they stay within the hive until spring. All that to say, they can't rely on vision for most of their activities. Their various dances (of which the waggle dance is probably the best known) are actually felt rather than seen. For this reason, I believe they could not rely on vision for mite hygene.
Note that Varroa is only one of the troubles that bees face! There are also hive beetles, wax moths, European foul brood, American foul brood and more, depending upon geography. Asian hornets are another serious problem in some regions.
Despite all this I would encourage anyone to look into beekeeping and see whether they find it interesting. I feel like I've discovered a fascinating and lovely niche with a great community around it, and I wish I'd gotten into it earlier.
You can interrupt whatever that varroa are doing with icing sugar. You shake a cup of bees with icing sugar in there. Anything above 2-3 varroa per cup of bees is the standard treatment threshold. It’s horrifying to see 15 fall off a cup of bees from a strong, healthy looking hive. Varroa are awful.
I’ve just noticed that for first pic in that article is labeled with a scale saying ‘200mm’ presumably it’s supposed to be .2mm (I cant get Greek on my phone).
There are so many ways they are treated for varroa all year round (except high season) with "chemicals". They were simply not forced to develop a distinct hygienic behaviour. But every treatment damages the hive and puts the bees on risk.
Thats why, in the last years, the selected breeding "movement" started growing.
Actually, several behaviors have already emerged. Bees can groom each other to remove the mites, and they can also display hygienic behavior where they open up cells with infected larvae and removed them.
Apis mellifera has not historically lived with Varroa, but it's close relatives have and they successfully developed a stable host-parasite relationship with the mites. Wild honeybees left alone have quickly (a decade or two) adapted to the mite to develop this same stable relationship. Insect generations are short which enables more rapid evolution. In this case, the re-emergence of some now strongly adaptive alleles.
There are many beekeepers today breeding honeybees with these specific behaviors in mind, to avoid the need for chemical treatments. This is not the norm, but it's taking on more importance in the face of an escalating arms race - mites can evolve resistance to chemical treatments, too. It's also not just these behaviors that help honeybees live with mites. Many of the ways humans keep bees commercially to make things easier for us actually make things harder for the bees.
The problem is that to fight against Varroa effectively, all the beekeepers in the area have to fight Varroa. That just doesn't happen, so I feel like natural selection will be the way out.
Not to mention wild bee colonies also have to be treated or eradicated.