Stoneflies require flowing water to live, and the highest population densities are found in cool, well oxygenated streams. During their lifecycle, they undergo incomplete metamorphosis, passing through only three stages of developement; egg, nymph and adult. Most of their lives are spent in the nymphal stage, which varies in length from seven months to four years. Mature nymphs crawl from the water and the adults emerge on land. Mating also takes place on land.
Egg-laying habits vary, but species that fly out over water and touch down briefly to release their eggs are the most important to anglers.
