Trout eat em on Hebgen Lake. After ice out, the midge hatches up to size 12 get so prolific that balls of midges roll across the lake surface, driven by the wind.
http://www.yellowstoneflyfishing.com/midges.htm
http://books.google.com/books?id=TMk...midges&f=false
http://books.google.com/books?id=OZC...midges&f=false