No argument need started..The Black Flies that appear on the South Holston are more commonly known as LBF's or Little Black Flies. It is a rather common hatch on this river as well as the Holston River, the Clinch River, and the Watauga River. Not sure on the Caney Fork but I'm sure Byron or Plateau Angler could give some insight. I've personally photographed these lil guys after retrieving stomach contents of several fish on the South Holston. Hugh Hartsell would be more punctual on this conversation as it relates to the Holston River, as he spent the last year attempting to "match the hatch" appropriately for one of his clients.
The little black fly is similar in shape to a common house fly scaled down to 1/4 of the size. The midge your refering too also habits many of our streams and tailwaters. Chironomidae have a much longer abdomen wings and much longer legs. This fly has the appearance of a mosquito which is why it can be a rather favorable "go to" pattern for this bug.
And if all that doesn't work here's a picture from the one I pumped on the South Holston
Black Flies are also rather common in the smokies if I'm not mistaken, at least in the heat of the summer my arms and legs feel the pain of this nasty lil "Buffalo Knat's" More commonly known on the Tellico River as "Dog D*&% Knats"