All Stoneflies, from the Little Yellow Stonefly to the Salmonfly, are all members of the Order Plecoptera. Members of this Order can be found all across the globe, except for Antarctica, and their lineage descends from the age of the dinosaurs. The Stonefly is truly an ancient master of the streambed. As a result of their long, mostly unchanged lineage, Stoneflies are fairly intolerant of water pollution and their presence, or absence thereof, is an indicator of the water quality of each waterway.
Most telling of a Stonefly is its wings, in fact the name Plecoptera is Greek and means “Braided Wing” and refers to the features of the wing and the many venations that run through the fairly opaque wing. Various species have evolved varying colors, but, with the exception of a few species, all have large wings that lay flat along the body. For many, though, the wings have become nearly useless and when they are used the Stonefly is clumsy under its own weight. Common characteristics of the nymphal stage include two claws at the end of each leg, two sets of wing pads, two short-heavy tails, two antennae, and they look fairly armor plated. General adult characteristic include two claws at the end of each leg, two pairs of wings held flat over the abdomen when at rest.
When it's time to emerge as an adult, the vast majority of Stoneflies migrate to the shore, climb out onto the rocks along the shore, and emerge from their nymphal shuck in the open air. During a "hatch" of stoneflies, the migrating stoneflies are vulnerable but their actual emergence is safe from attack. Not until the female, heavy laden with eggs, returns to the water to lay them, the adult Stonefly is also safe from attack.
Stoneflies are amazing bugs that, like their primary predator, are great indicators of the quality of water that we are fishing. If the old saying, "Big fish need big food" is true, then using a Stonefly is the key. As always, Good Luck and Guid Luck!
Nelson, Riley. "Clean water has bugs in it, says BYU Biology Professor Riley Nelson". Retrieved July 2, 2014.
C. Riley Nelson (January 1, 1996). "Plecoptera. Stoneflies". Tree of Life Web Project. Retrieved July 2, 2014.