Flight periodicities and vertical distribution of Aedes cantons (Mg.), Ae. geniculatus (Ol.), Anopheles plumbeus Steph. and Culex pipiens L. (Dipt., Culicidae) in southern England

Abstract

After preliminary collections with suction traps at heights of 30 and 135 cm had shown that most mosquitoes were caught in the lower trap, suction trap catches were made for three years from about April to November in a wooded area in southern England. Flight periodicities of females of Aedes cantans (Mg.) and Ae. geniculatus (Ol.) and of both sexes of Anopheles plumbeus Steph. and Culex pipiens L. were determined by traps incorporating automatic segregating devices. In all species maximum flight activity was between 19.00–20.00 h GMT. The biting cycles of the first three species were similar to their general flight patterns. Mean hourly densities of all four species were calculated from the suction trap catches. Collections were made with traps placed at five different heights (23–223 cm) in 1968 and at eight heights (23–550 cm) in 1969 and 1970. In most species there was a well defined and rapid decline in aerial density of both sexes with increasing height, but more unfed females and males of Culex pipiens L. and females of Culiseta morsitans (Theo.) were caught in the highest trap. From about mid-August onwards, when adults of Culex pipiens were searching for hibernation sites, both males and females with fat reserves were commonest in the lowest trap. The slopes of the regression lines of log. density on log. height were calculated separately for Ae. cantans and C. pipiens, and for all adults combined for five less common species. In all catches, except those of C. pipiens, unfed females predominated.