The TDC (Thompson's Delectable Chironomid) was developed by Richard B.Thompson in the late 1950's. Richard was a Fishery Biologist for the State of Washington. Prior to this fly, Chironomid fly fishing within lakes was just not done. Richard developed techniques with this fly, such as utilizing an indicator for depth control and fishing the pattern off the bottom of the lake with a slow retrieve. He wrote an article , "Chironomids and Trout" that was published within the State of Washington's Game Bulletin describing his TDC fly. Many tried using the Chironomid pattern but failed, due to their habit of using a fast retireve. However, by the early 1960's, his techniques caught on with other lake fly fishermen and a number of other Chironomid patterns were developed. His TDC pattern, using a dubbed body, remains highly effective and is the basis for many new variations.
During the 1990's, a local guide service in Mammoth, Sierra Drifters, developed a series of chironomid pupas and emergers for Crowley Lake. These were variations of the TDC utilizing Superfine dubbing for the body, a beadhead, and wire ribbing. The guide, Tom Loe, would add a strand of Pearl Krystalflash to the end of the pattern for attraction and refer to the pattern as a Crystal Midge Pupa. By adding Turkey Biots behind the bead, these variations became known as his Gillie patterns. Many of these patterns have transformed into a thinly dubbed body with a krystalflash overbody and wire ribbing. No longer do they appear to be similar to the TDC but have become a pattern within it's own. I have a webpage devoted to Sierra Drifter patterns.