DIEL PERIODICITIES OF EMERGENCE OF SOME HIGH ARCTIC CHIRONOMIDAE (DIPTERA)

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Abstract
The diel periodicities of emergence of seven species of chironomids from two ponds in the Hazen Camp area (81°49′ N., 71°18′ W.) are considered in relation to physical factors. Emergence of all species is greatest during the middle part of the day: an increase in water temperature induces emergence and a decrease inhibits it, whereas changes in light intensity, ultraviolet radiation, sunshine, and wind appear to have no effect on the diel emergence pattern. In a shallow pond, males emerge slightly earlier in the day than females in some species. In the same pond also, emergence, particularly of females, is sometimes distinctly bimodal. In a deeper tarn where the diel temperature fluctuation is very small there is a single peak, which is less pronounced than in the shallow pond.That temperature controls the periodicity of emergence implies that short-term temperature changes which may inhibit adult activity are of great importance in the high arctic. At these latitudes, changes in light intensity evidently do not reliably indicate to the emerging organisms temperatures which fluctuate near critical thresholds for activity.