Interesting behavior: appears to be attempted theft of pollen from the bumblebee worker by the honeybee. The honeybee was repeatedly landing on the bumblebee for at least a minute, and actually followed the bumblebee to a second flower on the bull thistle plant. On looking at the photos, it appears the honeybee worker was targeting the pollen clumps on the corbicula. She was not successful in removing an entire clump but did seem to be getting some of it off.