The Little Brown Stonefly group or Perlodidae family includes the Skwala genus of stoneflies that are found in the Rocky Mountains. They can start to hatch as early as March. These stoneflies are usually found in riffles and runs or just below them. After they hatch look on the banks near foliage for the adult Skwalas. They represent a huge hatch on the streams where they exist. Trout eat both the nymphs and the adult female eggs layers