The Fern Fly is an old British Pattern that was adapted in the US. As Mary Orvis Marbury reports it probably should have had a name change in the US to avoid confusion to the Fern Moth as in the US the pattern was made to replicate a moth like fly that clung to stream side ferns and other plants.
The Ray Bergman version is more in line with the insect the British pattern was designed to imitate.
Grey Wing Slips
Light Pink Body
Light grey Wing Slips
Both of these are tied on Mustad 3906 Size 8s