Agapostemon (green sweat bees) nest in the ground. They live in small social groups.
Ground nests often have several entrance holes; each must be guarded. This is a "job" for certain bees. Check out the two guard bees standing sentry. I consider myself very lucky they tolerated my presence here. Enjoy!
Aren't they beautiful?
This particular nest has two main entrances, pictured above. There is also a back door:
Thanks to the horticulture team at Red Butte Garden for this wonderful discovery!