Al Troth, a fly tyer from Pennsylvania, first tied the Elk Wing Caddis in 1957, trying to imitate both a caddis and a small stonefly. It was fished as a searching patterns, in hopes that this buggy, generally imitative fly would earn a good response, the rest is history. Like the Stimulator and the Adams, this fly is fished all over the world and has been tweaked and changed countless times, yet most tie the original because it has remained that effective.
In South Africa it is probably the most effective pattern across the board for yellows on the Vaal and Sterkies, and for trout in rivers and stillwaters. That's not to say there aren't more effective flies for each of those fisheries, because there are, but few are as versatile as the Elk Wing Caddis.