Moved from Tarantula Hawks.

Brian, to answer your question, there does seem to be a vague, pale darkening of the wing color just in from the hyaline tip...but that's not the distinct darkening usually referred to as "the dark submarginal band" in Pepsis thisbe.

Scrutining the full-size 1138x1254 pixel version of the image, the wing venation indicates this is indeed Pepsis rather than Hemipepsis or Entypus. (Also, the later two genera usually have body color thoroughly black with no bluish tinge or sheen...though there are exceptions.)

As for species, the lack of an appreciable dark submarginal band, the relatively pale, yellowish-cast of the orange of the wings, and the prominent metapleural tubercle, all point to Pepsis pallidolimbata.

The relatively thick, uncurled antennae suggest a male here, but the most dependable way to tell is to count the antennal segments (13 for males, 12 for females). Those are hard to make out here (easier in the full-size image), but I agree with Bob's comment below that there appear to be 11 flagellomeres (which...adding on the basal two segments, called the scape and pedicel...gives 13 antennal segments altogether).

The milkweed here is Asclepias subulata.

Moved from Pepsini.

Moved from ID Request.

Some of the male Pepsis thisbe seem to have the apical portion of the dark band somewhat light or almost missing. Let's wait for an expert. 11 flagellomeres = ♂
The anal portion of the hind wing is showing a very dark banding, along the lower edge of the right-side wing, folded on top of the left-side wing.