We were really concerned for a bit there. Was it some disease.
As we looked and observed the bees we could see they were healthy. And then I remembered a documentary from a long time ago about how certain flowers want to ensure that their pollen is spread.
Some flowers are set up with triggers and so when the bees enter or leave, the flower has internal parts that trigger to stroke, slap or spray a puff of pollen onto the bee.
What was most interesting is that the pollen on their thorax is really hard for them to remove completely on their own. If it was on other parts of their body they could wipe it off themselves and brush it into their baskets.
So the flower isn't just pretty--it's smart. It knows to brush the pollen into a spot where it won't get rubbed off easily, all the more to ensure it gets transferred into the other flowers of the same species that the bees will visit.
This summer I watched as most of my hives had bees coming back with white strips on their backs. Like skunks they were all entering the hive. I maaged to get some photos and video as well.