Going through some old photos, I noticed a number of shots of a tephritid taken within about 5 minutes of each other. I snapped them as the tiny guy flew from spot to spot on an interesting desert plant, Sticky Ringstem (Anulocaulis annulatus). Not until preparing to post them here did I realize there were actually two different flies...both species of Trupanea I think. The other fly is shown here. (Besides having different wing patterns, the two flies also have different eye-color...green here...though I don't know if that's significant, may change with lighting.)

I'm guessing this is Trupanea pseudovicina as a result of careful comparison with the wing pattern plates on pages 108-117 of "The Fruit Flies or Tephritidae of California", published in 1963 by Foote & Blanc (downloadable as a PDF here). I know that's not a conclusive method...hoping for feedback from other more experienced Dipterists out there (Martin, Ron,...?)