Pteronarcys (pronounced tear-a-nar-sis) dorsata is the largest stonefly found in the Upper Midwest trout streams. Its common name is the Giant Stonefly and out West it is called the American Salmonfly. The nymphs take 2-4 years to fully develop. So, these large morsels are trout food 24/7, all season long. In the cold-water trout streams of northern Wisconsin, you can find these big nymphs underneath decaying logs and branches in the shallows. Pteronarcys stonefly nymphs feed on detritus and diatoms….