Identification manual for the larval Chironomidae (Diptera) of North and South Carolina
By John H. Epler
Epler, J. H. (2001). Identification manual for the larval Chironomidae (Diptera) of North and South Carolina, North Carolina Department of Environment and Natural Resources, Division of Water Quality.
Keys to genera of Chironomidae of North and South Carolina, but works pretty well anywhere in the country. Also keys to species for many genera. I use this along with the Chironomidae chapter in Merritt, Cummins and Berg as well as the Wiederholm Holarctic larvae book.
PDF available at John Epler's website among other places:
http://johnepler.com/SEMidges.pdf