We have an over abundance of bumble bees in our garden. Anything that is blue they seem to be attracted to. A bee on a Vitex bush in first photo.
5th photo is of the very tiny blue flowers on a Blue Sage also know as Big Sage with one bee right in the center of the photo. (the round blue object is a bird bath.)
Although most of the bees were after the blue flowers I did find one on an almost gone zinnia blossom. We hadn't had a lot of problems with these bumble bees even though there has to be several hundred buzzing around until this morning. Lee was watering a Vitex bush when one went up his shirt and stung him on the back. Some solercane spray seemed to take care of the sting. (no, I didn't find a stinger in it)