This pupa pattern was developed by Gary LaFontaine around 1974 subsequent to a three year period in which Gary used Scuba gear to study caddis within the Big Hole River of Montana. This fly pattern represents the caddis once it is in the surface film. Gary noticed that caddis pupa were vulnerable only when the pupa was cutting itself free from it's cocoon and under the surface layer where it splits it's pupal shuck. Gary found that only rarely will a trout feed or chase the pupa during it's time of ascent. When the caddis pupa cuts from it's cocoon, there is a 15-20 second period in which the pupa drifts along the bottom generating gas to fill the sheath around it's body. This gas produces a shimmering effect to the pupa. The ability to mimic this shimmer was critical to Gary's pattern and he accomplished that effect by using Antron fibers developed by DuPont in 1973. Antron is a trilobal fiber-yarn that is resistant to matting and has the ability to hold air bubbles within water. By utilizing the Antron for the underbody and a sparse overbody, Gary was able to accomplish the gas-attracting qualities of the fly and the translucency required. Gary noticed that while this emergent pupa pattern is within the surface film, the overbody will develop at trail of small bubbles that also acts as an attractor to the fly. Ralph Cutter in his book, "Fish Food" (2005) suggests coating the fly with powdered floatant as a means of creating bubbles around the body. He applies a split shot to compensate for the additional floatation.
The Emergent Sparkle Pupa can be tied in many colors. The original Sparkle Yarn that Gary used was a blend of a particular color and clear Antron. Clear Antron is no longer available, so many tiers will create a blend using White Antron. Eric Slagle, a quide from Montana, wrote an excellent article on using Antron Dubbing color blends in Fly Tyer , Spring 2006. He would use the dubbing for the overbody as well as the underbody. For the Sierras, Brown/Green are preferred during the months of April through September. The Brown/Orange is an excellent October Caddis pattern during the months of September and October. Usually the pattern is fished as a dead drift, although Gary usually liked to use some short mends while it was drifting.