Carpenter bees are notorious nectar robbers. Their big body makes it hard to fit into some flowers and they will drill or cut into the corolla of a plant to get at the nectar.
The stinkers are cheating the flowers; they get the nectar without a pollen transfer. I am not too worried, pollination must be happening, there are plenty of offspring.
The next time you're in the garden check the corollas on the tubular plants (penstemon, salvia, cuphea) for evidence that the nectar robbers have been there.
PS You can read more about Carpenter bees here and here.
Gail Eichelberger is a gardener and therapist in Middle Tennessee. She loves wildflowers and native plants and thoroughly enjoys writing about the ones she grows at Clay and Limestone. She reminds all that the words and images are the property of the author and cannot be used without written permission.