Emergence patterns of large stoneflies (Plecoptera: Pteronarcys, Calineuria, Hesperoperla) in a Montana river

Authors

Andrew L. Sheldon, University of Montana, Missoula

Abstract

Emergents of Pteronarcys californica, Calineuria californica, and Hesperoperla pacifica were captured with replicated emergence traps at 3 sites along the banks of Rock Creek, Montana. Pteronarcys emergence in early June was short (88% of individuals in 6 d) and attained rates of 5 m⁻¹ d⁻¹ (shoreline distance) and cumulative densities up to 19 m⁻¹ yr⁻¹. Calineuria emerged synchronously (89% in 9 d) 2 wk later at densities up to 7 m⁻¹ d⁻¹ and 40 m⁻¹ yr⁻¹. The less numerous Hesperoperla (5 individual m⁻¹ yr⁻¹) had a longer emergence period partially coinciding with Calineuria. Median males of Pteronarcys and Calineuria emerged 2–3 d before median females; protandry was not significant in Hesperoperla. Sex ratios were female-biased in Pteronarcys and Hesperoperla but male-biased in Calineuria. Size trends through emergence were very weak although females showed a greater tendency toward larger size early in emergence.

Recommended Citation

Sheldon, Andrew L. (1999) "Emergence patterns of large stoneflies (Plecoptera: Pteronarcys, Calineuria, Hesperoperla) in a Montana river," Great Basin Naturalist: Vol. 59: No. 2, Article 8.
Available at: https://scholarsarchive.byu.edu/gbn/vol59/iss2/8