Great Basin Naturalist


During a physiological study that required the collection of several thousand stoneflies, Pteronarcys californica, observations were made on the distribution of these aquatic insects within streams. It was noted that P. californica occur primarily in large rivers that have loose, unconsolidated substrates and swift currents. They occur from depths of six inches to several feet. They are exclusively vegetarian, feeding on detritus, algae, and diatoms. P. californica congregate in dense clumps, but within the clumps they segregate by size. The largest specimens are found in the quietest water. There is evidence of some seasonal variation in their behavior.