SEASONAL EMERGENCE AND ACTIVITY OF MOSQUITOES (DIPTERA: CULICIDAE) IN A HIGH-ARCTIC LOCALITY

Abstract

AbstractThe emergence and adult activity ofAedes(Ochlerotatus)impigerandA. (O.)nigripesduring 1962–66 at Hazen Camp (81°49′ N., 71°18′ W.), Ellesmere Island, N.W.T., are described.The greater part of seasonal emergence (assayed by emergence traps) took place from shallow ponds during a period of 7–10 days, usually in early July. Emergence ofA.impigerbegan about 3 days earlier than that ofA.nigripes, and peak emergence of the two species was separated by about 4 days; males of both species normally emerged 1 or 2 days before the females. From each pond 80% of annual emergence usually occurred within 3 or 4 days. Pond-to-pond differences were correlated closely with water temperature, but delayed emergence occurred at the end of the emergence period in temporary ponds, as the ponds became dry. Year-to-year temperature differences altered both the seasonal position and the duration of emergence in a given pond by up to 10 days.The flight activity of adults (assayed by a Visual Attraction Trap and a Malaise Trap) was greatest shortly after the period of greatest emergence, but adults, especially females, were caught for more than a month after emergence had ended. Biting by females continued throughout this period, but swarming of males was more abbreviated, especially inA.impiger. The number of adults trapped fluctuated from day to day according to weather: flight was inhibited when maximum screen air temperatures were below about 5 °C. The interval required for ovarian maturation was about 9 days in both species, and some females completed at least three gonotrophic cycles. The successive cycles were detected in the population by analysis of sweep-net catches, the proportion of gravid females caught in the traps being affected considerably by weather. Successive gonotrophic cycles were well synchronized, like emergence, inA.nigripes; retention of eggs apparently obscured such synchrony inA.impiger.Feeding on nectar (of the flowerDryas integrifolia) was apparently needed by both sexes to maintain activity, at least upon emergence.Year-to-year differences in the numbers of adults emerging were correlated with the amount of flight, and hence reproductive activity, permitted by weather the previous year.These findings are summarized graphically (Fig. 21). Critical comments are made on the usefulness of some of the sampling methods employed. Some characteristic biological features of arctic mosquitoes, leading to prompt emergence in spring and permitting subsequent reproductive activity despite the low temperatures and variable weather of the summer, are discussed.