The Life History and Ecology of the Stonefly Neoperla clymene (Newman) (Plecoptera: Perlidae)1

Abstract

Semi-monthly samples of Neoperla clymene (Newman) populations were made from November 1970 to October 1971 in the Brazos River, Texas. Emergence occurred May through July. Mean fecundity of females based on dissection was 646 eggs. Females deposited up to 3 egg masses in the laboratory. Field-collected females deposited an average of 173 eggs per mass. Eggs required incubation at 24±2 C and 15 hour photophase. Nymphal growth exhibited 3 phases; males and females underwent 18-20 and 20-23 instars, respectively. The greatest growth occurred during the spring. Standing crops ranged from 21.5 individuals /m² in July to 225/m² in May. Stomachs of 443 nymphs, during spring growth, contained primarily Trichoptera eggs, Cheumatopsyche larvae, Neochoroterpes nymphs, N. clymene eggs, Chironomid larvae, Simulium larvae and nematodes; nymphs predominately fed at night. Utilization of Ivlev's Electivity Index showed preference in feeding for Chironomid larvae and pupae, Elophilia larvae, Chimmarra and Cheumatopsyche. Significant overlap in feeding occurred between N. clymene and the associated insectivore Corydalus cornutus during March and April.