The Two-spotted Digger Bee Melissodes bimaculata is named for the white patches on each side of the abdomen of the female. The males showed up first, (no patches) on English Lavender and Purple Giant Hyssop, around July 15 last year (2016). At night they slept by hanging on to the leaves of Obedient Plant Physostegia virginiana.
By July 22, the Cuckoo Bees Triepeolus lunatus showed up, at least 5 females and 1 male. They all hung around the Black-eyed Susan (Rudbeckia hirta).
Triepeolus lunatus females hunt for the Two-spotted nests and lay eggs in their cells. When the Cuckoo larva hatches, it either eats the egg or the larva, and then feeds on its nectar/pollen mixture stored in the cell.
The Two-spotted females showed up around the first of August, favoring the Giant Purple Hyssop and were quite attracted to the pollen on Big Bluestem. They spent the night in their nests near the Obedient Plants.
But the others all slept together on the Obedient Plants! Both the male and female Cuckoo Bees and the Two-spotted males. Not on the same leaf, but very close and quite comfortable with each other.