These are very nice photos. My comments are in no way critical of them, nor of what viewers find particularly interesting. I think these are carpenter bees, another, quite separate family of bees than bumblers. They gouge long tunnels in wood and fill them with a series of leaf-wrapped pollen with single eggs, separated by barriers of chewed wood and dried saliva. Then they leave to repeat the process again in a new, laboriously gouged tunnel. Interestingly, the oldest will be at the inner end of the tunnel, and will mature first. All the new-bees will wait patiently for a week or so, then start to wriggle around, and this will alert all to start to dig their way back out of the tunnel. Any who are late in maturing or have died will get chewed through in the process, and all the live ones will exit in a row. The eye patterns are formed by the reflections in the eye itself, not reflections of the flowers, a characteristic of this family of bees, like bare black abdomens, unlike bumbles. I think yours are males, they seem to have yellow patches below the antennae; females have black there.