I keyed this in Hull(1) and it went unambiguously to the genus Geron. I have no idea which species though, and comments on other BugGuide Geron posts indicate that determination of species in this genus typically requires examination of genitalia...oh well :-) At any rate, they're elegant little bombyliids!

This one was resting here between foraging forays on the desert shrub Psorothamnus polydenius, in the pea family (Fabaceae). I presume it's male from the holoptic eyes (best seen it subsequent images in this series).