Thank you for the quick response.

It was picking at rocks. As it was pulling on the rocks it made a squeaking noise. It was neat to watch, but it made me nervous.

I am not sure what characters are diagnostic but I will load a few more photos in hopes narrowing it down further.

This reminds me of a really stocky specimen of Palmodes, but I'd need to see her with prey to be more sure:-) I'm not sure what other genera are up there in Utah. Pretty certain this is not the genus Sphex, but I still can't rule it out. Update: Moving to genus page. I'm confident enough, but willing to take flak if I'm not correct:-) If you see another one of these, please catch the thing! Much easier to ID an actual specimen. Thanks.

I live in the deserts of southeast Idaho, very similar to utah, and have a specimen very very similar to your picture here. In fact, Im certain that it's the same species. I could post pictures somewhere of my specimen if you would like Mr. Eaton. Ive got it in my collection.