I have a lot of bumble bees around my Salvias, and they are relatively harmless, unless they are in their nests and you cover up their exit with your hand by accident. You will get a bite which will disappear after fifteen minutes unless you have an allergy or sensitivity to stings.

For many on the east coast, these are usually carpenter bees, with shiny black bums. They bore half-inch holes in wooden structures like my nursery tables, Which are made from pressure treated 2 x 4 timber. Their exit holes are on the lower surface, which are not in my field of vision. They can be rather damaging to building eaves and other exposed wooden horizontal structures facing the ground. They also are pretty rough on long-tubed flowers like Salvias and will prevent seed set.

When flying, they may dart and hover in front of you, but a wave of your hand will send them flying. You will also see the males darting and diving after each other, similar to feuding male hummingbirds.

I didn't think that Bumble Bees even had a stinger. The old gardens had hundreds of bees of all sorts at all times and I never, ever got stung... not did anyone else! I just told them to stop swatting and walk slowly.

With mandibles that can chew through solid wood, they can bite pretty effectively. So can ants and many wasps.

Rich wrote: "carpenter bees, with shiny black bums...are pretty rough on long-tubed flowers like Salvias and will prevent seed set."

They prevent seed set by bitting a hole at tube bottom to easier access nectar and all other bees follow zapping sophisticated salvia pollinating mechanisms.

Most bees have stinging habilities but most often rely on size and noise deterrence.

Carpenter Bee venom has curious effects, not very painful it makes one intoxicated somewhat as if drunk.

The only reason to "do something" about bumble bees that I can see, would be if a resident or frequent visitor is scared to death of them or at risk for anaphylactic shock from a sting.

I've found bumblebees to be harmless. One possible exception is if you're handling the plant and don't notice one asleep in a flower.