Sparnopolius confusus--this bee-fly gave me fits. I saw what I think was this species on the 2011 trip, but did not get diagnostic photos, and I was not sure what it was, other than the family. This fly was rather sluggish in the cool morning, and I got photos showing the wing venation--critical to ID most flies. I was able to compare this in detail with photos at BugGuide and Herschel Raney's online key for this family in the East. I posted a series of detail photos at BugGuide as documentation. (last link now corrected)