This cyclical pattern of behaviour is
initiated by only a short exposure to light (Gillett, Corbet & Haddow, 1959), and experiments with a Southern Nigerian strain showed that a single exposure to light for five seconds of females reared and maintained in darkness was sufficient to allow the return to darkness to be a time-cue for initiating a 24-hour oviposition cycle (Haddow, Gillett & Corbet, 1961).