The GT apparently stands for "Go To". Designed to "imitate natural mayflies struggling from their shucks on and below the surface" (pulled that off the MFC site). Looks to me like Rich forgot to tie the tail in first and is just covering up his mistake; nice save. Tied here in PMD colors; change to suit your needs.
hook - Dai Riki 125 #16
thread - MFC 8/0 light olive
shuck - biot PMD
tail - hackle fibers ginger
wing post - Congo Hair white
hackle - ginger
thorax - Spectrablend PMD
Part 1
mash barb, start thread and wrap halfway down the bend
moisten biot; I prefer the raised rib so I tie it in notch-side down
wrap biot to point above point and tie off
even tips on some hackle fibers, measure for length (gap width past bend) and tie in
tie in a hank of CH; post and tie in hackle, shiny side out