Diel Periodicities of Emergence and Oviposition in Riverine Trichoptera

Abstract

Diel periodicities of emergence and oviposition of Trichoptera, observed in the St. Lawrence River at Montreal, Quebec (451/2° N.), in late June and July, are closely similar. They are poorly synchronized but the peak for most species is nocturnal, falling between sunset and solar midnight. Catches in floating traps were used to measure emergence rate. As such catches (of Trichoptera) may contain parous as well as newly emerged females, attempts were made to separate these two components of the catch before analysis, thus providing records for both emergence and oviposition. Oviposition periodicity was studied independently by counting egg-masses on a floating board. Precautions needed for future critical work on emergence are mentioned.