Diel Periodicities of Emergence of Midges (Diptera: Chironomidae) from a Wooded Stream on the Niagara Escarpment, Ontario

Diel emergence patterns of ten species of Chironomidae from a spring-fed, woodland stream (the Windrow Farm stream) in Southern Ontario, Canada are described. All species conform to one of three patterns of emergence, unimodal, bimodal or amodal. The effects of light-and temperature-induced emergence cues are discussed. The results of this study are compared with those from other temperate and arctic streams and it is suggested that both light and water temperature changes influence emergence patterns but that endogenous rhythms established during larval life may also play a part. The apparent absence of protandry and sex ratios of emerging adults are also discussed