Sand Wasp (Bembix sp.)
A few photos of a striking wasp from the Bodega Dunes. [This may be Bembix americana comata, but I don't have any experience identifying this group.]
Most individuals were black and yellow, but some had white stripes instead of yellow (see below). Note the bright green eyes and dramatic yellow legs.
These solitary wasps are found in open sand areas. Females dig burrows for raising their young. The female captures and kills a fly, brings it to the burrow, and lays a single egg on the dead fly. After the larva hatches the female continues to provision the young, bringing food to the developing larva.
Here's a photo of a female actively starting to dig a burrow. Look for the sand flying backwards.
Here's a single burrow entrance. Several burrows may be located adjacent to each other.
I'm not certain, but I think this is an old pupal case in which the larva undergoes metamorphosis into an adult. I sometimes find these neat capsules on the surface of the sand. Are they exposed by erosion? Do predators dig them up?
P.S. For any wasp enthusiasts who haven't already read Wasp Farm by Howard Evans, I highly recommend it!