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

TLDR: The seasonal abundance of the nymphs was controlled mainly by factors associated with life-history phenomena and temperature had some effect on these phenomena but was not the only factor involved, especially in the headwaters, where temperatures were nearly constant.

Abstract: The life history and ecology of Epeorus pleuralis in Morgan's Creek, Kentucky, were studied over a 20-month period beginning February, 1963, and continuing through September, 1964. E. pleuralis has a univoltine life cycle. Hatching begins in late September or early October and extends through May, with a peak in January or February. Emergence starts in late February 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. The nymphs are herbivorous and eat principally allochthonous 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.