A cicada killer indeed. It is a solitary wasp, meaning it doesn't defend it's nest like yellowjackets and hornets do. This means they won't attack you, and as ccabal said, it is quite harmless unless you physically harm it or get tangled up with it somehow. I'll tell ya though, I got some serious goosebumps the first time one of those things flew in front of my face, because I had no clue what it was. Joe

Look at my post "Bees or imitators" a few posts down. I wonder if we have the same type. I think mine only have one set of wings and I believe bees have at least two set of wings. I think hover flies have one set of wings and look like bees. They seem to dig in the dirt but only on the surface. I don't see any burrowing done by mine. They don't buzz and they don't seem to mind me deadheading my petunias.

Where do you live? There are many ground-dwelling "solitary" bees. they are good pollinators and not aggressive.

To see them active and identify them, they need to be active during that time of year and it should be relatively sunny and warm out. As it's winter as I write this, if you have a way to remove the tubes, you can open one up and examine the cocoons - sometimes you can tell by the shape and the composition of the mud dividers. You can take tiny scissors too and open up a cold cocoon. The occupant will be hibernating so may only move a little bit, but certainly won't scramble around and fly as long as it stays cold. If you can get access to any of that, try googling "solitary bee identification". Everyone talks about a handful of osmia species, but there really are hundreds of native bees that nest like that. The Utah Bee Lab in Logan may be able to help identify them from photos.