Thank You, Aaron.

[Charles...a prefatory disclaimer here. Please don't feel obliged to read and/or respond to my notes here if you happen to be one of the many folks who are not especially into the technical details of taxonomy. I write comments like these under interesting posts for the relatively few who are keenly interested and curious about the technical details and nuances of species ID. I do so in order to summarize and share what I've learned in my own study efforts. My intention is to help others who may be "interested in all the details" to learn...and not to torture those who may not be! So, read on only if you enjoy such things :-]

In my earlier comment above, I speculated the wasp in this post might be P. chrysothemis...since "if this were a female" the wing coloration (especially the details of the dark border) would be a fairly good match for that species. I made that statement, even though I could see this is not a female, but a male. My point was that in many (but not all!!) cases, the wing coloration details in Pepsis are pretty much the same for females and males. That general idea is supported by the following quote from pg. 276 of Hurd(1)(1952):

"Perhaps the most diagnostic color characteristics of the wings are the nature, extent, and placement of the exterior marginal and submarginal dark bands. [...] In general, there is little if any lack of correspondence between the sexes in the extent or placement of these bands."
The problem with my application of this principle above is that...as it turns out...P. chrysothemis is the main exception to the rule! The above quote from Hurd(1)(1952) continues as follows:

"However, in the xanthochromatic species chrysothemis, there is an important sexual difference in this respect. The forewings of the male are, at the extreme apex, very distinctly though narrowly whitish hyaline, while the apices of the female wings are uniformly dark and indistinguishable from the coloration of the exterior marginal dark band."
So, since this is a male (since I can confidently ascertain 11 flagellomeres when zooming in, and also the antennae are relatively straight); and since there are no hyaline tips on the wings, the above quote rules out P. chrysothemis in this instance.

Revisiting the possibilities, my (revised) best hypotheses on the species here are either: P. mildei (as you perhaps intially believed when you posted it?); or P. angustimarginata...the latter now being synonymized under the name P. basifusca per Vardy(2), "Part 3", pg 141.

I invite the curious reader to scrutinize the detailed descriptions of these two species on pp. 288-293 of Hurd(1)(1952). They both fit the characters visible in this photo (including a prominent mesopleural tubercle) better than any of the others...provided one notes that Hurd mentions some P. mildei have the entire antennae black! Note also that the Henryetta, OK location here is nicely within the range of P. mildei, and there all also records not too far off in Kansas and Arkansas for P. angustimarginata (see the range maps on pp. 290 & 292).

I think the above two are the best candidates for species here, after reading and rereading the detailed descriptions in Hurd(1952) of all 14 of the current US species of Pepsis, and getting a basic feel for the particulars of wing coloration (especially patterns of marginal, submarginal, and humeral dark bands for the orange-winged species); of antenna color; of prominence (or lack thereof) of the mesopleural tubercle; of geographic distributions; and various other characters that can (with luck) be discerned in photos.

Aaron;
Thank You I really appreciate Your comments even though some are way above my pay grade.