This buzzed down onto the ground on a cool spring day. I was sure it was a bee, then looked more closely. I picked it up and placed it on a picnic table for some photos and measured it. Thanks to Eric Eaton for correcting my (mis)identification, and to Martin Hauser for a further, and interesting correction--see comments.
(The yellowish dots are pollen grains from deciduous and coniferous trees--ubiquitous at this time of year.)
Here is the exact location, I think: 36.073828,-79.00678
Image updated 3/18/18.
This site seems to be good for rare flies--this was found very near where Roger Rittmaster and I found a Ceraturgus
Update 4/27/14: This, and our other record to date, look to be males, with their holoptic eyes. An apparent female, with dichoptic eyes, is here
, listed under the (synonymous) C. johnsoni.