Yesterday, I saw two huge bumblebees (maybe they were normal-sized, but I was nervous about them) chasing around a parking lot. I don't know if one was chasing the other or they took turns or they were doing the bumblebee version of hanging out. They stayed within a few inches of each other most of the time, and they were moving pretty fast.
Territorial behavior? Mating? Bees are weirder than I know?