So the bees flying around the top of the butterfly bush aren’t miner bees after all. The miner bees are somewhere else.
One of the bees on the bush lit on my hand and when I got a close look at the photos, I recognized the cuckoo bee of genus Nomada. These are bees that exploit nests built by other bees, such as miner bees of genus Andrena. Hmm. Where there are parasites, there must be hosts not far away.
And sure enough, I found a miner bee of genus Andrena on the ground. (That bit of red is a plant shoot, not part of the bee.)
This bee was born underground where it ate up a ball of pollen and honey left for its sustenance. It spent the winter as a pupa, and now that the weather is finally warming up, it’s out and about, enjoying the bright afternoon sun, ready to start the next cycle of bees.