Modification of circadian flight activity in the mosquito Anopheles gambiae after insemination

Abstract

THE flight activity of female Anopheles gambiae Giles, recorded in the laboratory, follows a bimodal cycle¹. In LD12:12 (alternating 12 h light:12 h dark) the first peak comes shortly after light-off and there is a secondary phase of activity which reaches its maximum in the middle or latter part of the dark phase. This secondary activity occurs at the time when host seeking and biting take place in the wild²; the initial peak corresponds with the time of egress of mosquitoes from their daytime resting places and, in particular, in virgin females, with the time of mating³. In normal conditions, A. gambiae females are inseminated only once in their lifetime^4,5, and usually not before they are 2–3 d old (ref. 3). We show here that, after insemination, the first peak of activity is greatly reduced and the secondary phase of activity is enhanced. This switch in activity is likely to represent a change from mating to host seeking behaviour.