After nursing the stings, and allowing what I hoped would be enough time for the buzzles to calm down, I returned to the scene of the crime, and here's what I found.
If you look closely at the bottom of the stump, you can see the nest and
the little cluster of "alien pods," each containing a Bumblebee larva.
I felt terrible for disturbing the nest. And, in order to at least turn this into a teachable moment, we cordoned off the area and encouraged our guests to peer inside. And now, I'm sharing this unique view with you, totally sting-free! :-)
A closer view reveals a glimpse into the bizarre and fascinating lives of Bumblebees.
From the Bumblebee Conservation Trust: When she has chosen her nest, the queen will begin to collect pollen from flowers, to bring back to the nest. She forms a mound of pollen and wax (which she secretes from her body) and lays her first brood of eggs. She also collects nectar which she stores in a pot-shaped structure made of wax which is positioned in front of her mound. The queen keeps the eggs warm by sitting on her wax ‘nest’ and shivering her muscles to keep warm.
Sipping from the nectar-pot gives her enough energy to incubate the eggs for several days until little white grub-like larvae emerge. These larvae are fed on pollen and nectar which the queen goes back-and-forth to collect from nearby flowers. Once they have eaten enough, after around two weeks, they spin a cocoon, inside which they develop into adult bees. Read more, here: https://bumblebeeconservation.org/about-bees/lifecycle/
I encourage you to do your own research on the life history of Bumblebees. They're incredibly fascinating, and the process of sex determination sounds like something from an episode of Star Trek! (Google search "Haplodiploid.")