Feenstra's Halloween Leech This is Kevin's black and copper swung fly for steelhead. Over the course of many years, this is a go to fly that works year after year. Often times, when fishing two clients, it is fished interchangeably with the grapefruit leech. It is a safe bet that one of these two patterns will take fish. The Halloween Leech is at its best in October-December and again in the spring.