Allan I have heard people complain that they can't catch fish on the pupa or emergent. When I inquire about the materials used the usual reply is Antron yarn. I can only suspect that the proper yarn has fish catching appeal. That said I carry many different types or styles of caddis patterns. The sparkle yarn I use was purchased at a Ben Franklin store probably 30 years ago. It is to my recollection sparkleaire, I also have dazzleaire which is somewhat a softer texture yarn.
Gene