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Stoneflies belong to the order Plecoptera ('downwings'). Like the mayflies, these aquatic insects have been around for over 200 million years - 100 million years before the earliest recognizable ancestors of salmon and trout appeared on earth.
Stonefly nymphs are common inhabitants of the fast-flowing rocky stretches of streams (hence the name) and are usually restricted to well oxygenated, cold, tumbling mountain streams or riffle sections of cold unpolluted waters. A few species are also found in northern or cold lakes which have considerable wave action. Key features of stonefly nymphs include: Depending on species and habitat, stonefly nymphs come in various shades of yellow, orange, brown and black. Stoneflies have what is known as an incomplete lifecycle which consists of three stages; namely, egg-nymph (larvae)-adult. Nymphal development may be one year, occasionally greater. When mature, the nymph crawls from the stream onto land where it molts to emerge as a winged adult. The adults resemble the nymphs, but in addition have two pairs of elongated, heavily veined, wings which typically are held flat or occasionally wrapped partially around the abdomen at rest. A few species have reduced or absent wings. Adults tend to be weak fliers, which presumably explains why they spend so much time hiding under logs or rocks, or clinging under leaves and other streamside vegetation. Adult stoneflies tend to live longer than adult mayflies; but not by much. Instead of days, most adult stoneflies live a few weeks. During this short time, the adults mate, and the females lay eggs. Some species lay eggs by dive bombing into fast flowing waters; others simply crawl back underwater to deposit thier eggs. Stoneflies are generally recognized as being important food source for trout and salmon inhabiting coastal streams - they are present year round, and they can be found in the highest alpine streams down to the estuary. The flyfisher can expect to find at least 60 kinds (species) of stoneflies in Western coastal streams. It is not necessary to learn to recognize all the stonefly species; nor is it that useful to memorize the various generic groups, but I do think it is worth while to have a simple working classification for fishing purposes. One such classification, developed for species found in the Bella Coola river is listed below, together with emergence times.
2. Little Black Stoneflies: 3. Big Golden Stoneflies: 4. Rolled-winged Stoneflies: 5. Medium Brown and Yellow Stoneflies: 6. Early Black and Brown Stoneflies: 7. Little Brown Stoneflies: 8. Giant Stonefly (Salmonfly):
This simple classification is particularly useful because all one has to do is recognize that the insect is a stonefly, then the pattern used is based on color of the nymph or adult. By Harvey Thommasen with photography by Mike Wigle |
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1. Little Green and Yellow Stoneflies:
