Found visiting flowers of "prickly poppy" (Argemone munita), a native annual in the Papaveraceae. Other visitors (i.e. bees) were present, I hope to post images of some soon (I think some may have been Perdita).

I keyed this to genus Zodion in the Manual of Nearctic Diptera(1) and Camras & Hurd(2). Critical characters are: Antenna with dorsal arista; anal cell (or cup) longer than basal medial cell; proboscis not geniculate (I figure you'd see a thicker "doubling-over" of the proboscis in the images if it were geniculate); wing with 1st posterior cell (r5) open; femora without spines on apical half.

I was unable to key conclusively to species using Camras & Hurd(2), my best shot there being either Z. americanum or Z. cinereiventre. Images of Z. americanum presently on BugGuide look quite different to me, though Camras & Hurd mention it's a highly variable species. At any rate, according to the remarks on the first page of the 1943 paper by Camras titled: "Notes on the North American species of the Zodion obliquefasciatum group" (see this BIOSTOR link), the light thorax with relatively narrow dark stripes in this fly seem to indicate it's in the fulvifrons group. If I can obtain the following paper, I may be able to make progress towards species ID:

Camras, S. (1944), "Notes on the North American species of the Zodion fulvifrons group (Diptera: Conopidae)". Pan-Pacif. Ent. 20(4): pp. 121-128.