Life History and Ecology of Epeorus pleuralis (Banks) (Epemeroptera: Heptageniidae)

Abstract

The life history and ecology of Epeorus pleuralis in Morgan''s Creek, Kentucky, were studied over a 20-month period beginning Feb., 1963, and continuing through Sept., 1964. E. pleuralis has a univoltine life cycle. Hatching begins in late Sept. or early Oct. and extends through May, with a peak in Jan. or Feb. Emergence starts in late Feb. or early March and continues into June, with a peak in late April or early May. Growth proceeds during the winter despite very low temperatures. Thenymphsareherbivorousandeatprincipallyallo-chthonous leaf detritus, with some diatoms. The nymphs were most abundant in a cascade near the spring source of the stream. Their longitudinal distribution in the stream was largely determined by the interplay of temperature, substrate, and current. They were restricted to cool-water areas and to fast-water habitats, such as riffles and cascades. They were found mainly on loose, rubble substrate. The seasonal abundance of the nymphs was controlled mainly by factors associated with life-history phenomena. Temperature had some effect on these phenomena but was not the only factor involved, especially in the headwaters, where temperatures were nearly constant.