Found shortly after dark wandering around the sparsely vegetated sandy area south of the main (pure sand) dunes at Kelso.

At least one male was agitatedly flying in circles around this female when a flashlight or headlamp was shining on her:

   

But when I moved the light off the female the male completely ignored the female and frantically followed the light! (It was a full moon night, just in case that may be of relevance.)

Initially I had guessed this male/female pair might be Dasymutilla sackeni or D. satanas. But the head here has no long pile...whereas all the current BG posts of those species have long pale-colored pile on the head (except for this one).

Hopefully Kevin, George, and/or others may be able to shed more light on the ID here.