This is a series of images of adult bees; their access hole; larva; pollen food packet & nest chamber. From what I observed I believe they build several individual pupal(?) chambers radiating outward from the entrance tunnel and supply each with a packet of pollen. Found in moist well drained soil under a perennial plant like a rose bush. There were maybe a 2-3 dozen adults associated with this nesting site. None attempted to sting me, even though I was excavating their nest site in an attempt to extrapate Purple flowered Nutgrass from my rose garden.