This fly was found feeding on dwarf sumac (Rhus copallina) in the company of several sphecid wasps. Size estimated. This fly has me flummoxed. Looking at the wing veins, I think it is a syrphid, though I could well be wrong. I browsed through syrphids for some time, and I don't see anything too close, but it perhaps resembles a Copestylum (or the similar genus Volucella. It is now rather rare to find an eastern syrphid of which we do not have photos here on BugGuide.
Any ideas are appreciated.

Further speculation, please to call it "research":
North Carolina State University has Copestylum vittatum listed from the state in that genus (13 specs.), and four species of Volucella: bombylans (6 pinned), pallens (3), pusilla (2), and vesicularia (39).
Brimley (1) lists V. sexpunctata from nearby Raleigh in July and August--this sp. is apparently now Copestylum sexmaculatum (ITIS)--odd that it is not listed in the NCSU collection.
Brimley also lists V. vesiculosa from Raleigh, April-September.
Oh well--I may be barking up the wrong tree entirely.
(See comments below.)

Syrphidae of Oklahoma says male has holoptic eyes in genus Volucella (now would be Copestylum), so this must be a female.

WARNING--GRATUITOUS NATURE GEEK CELEBRATORY MOMENT
YEEHAW!--a new species for the guide!
(Thank you for your indulgence.)