have constructed these miniature sedimentary towers, so-called turrets, only a couple centimeters (less than an inch) high as entrances to their subterranean nests. These are the same bees (Diadasia diminuta) that collect pollen from the desert globemallow plant (Sphaeralcea ambigua). Industrious little diggers!
Bees exit the nest in a backwards direction. In doing so they lift loose sediment out of the turret on their backs.
Fully loaded pollen tanker returning to the nest.
For macro photography you must get CLOSE to the subject, and in this case, down on your belly!
Mallow bee in a globemallow blossom gathering pollen.
Here are a couple of good articles about the ground-dwelling behavior of the globe mallow bee and about the rose-mallow bee.