Sunday loungin' on the patio, I see a pretty decent sized critter hole in between the stones. Hmmm, I wonder. What made that? So, I fill it in with the surrounding pebbles and grit, and I wait. I mean, I'm only Sunday loungin', I've got the time, and the inclination. After a while, this big, creepy wasp looking mother-f'er crawls out, starts cleaning up her yard. (She's very prompt and diligent, that's how I know she's a she.) I'm actually seriously impressed with her method of excavation. She's moving fairly large pebble chunks with her face. Spreading the whole area out very methodically before she goes back in the hole for more. Pretty cool. I watched her for about 20 minutes.
Then I filled it back in again.