Fig. 1. Fifteen hours of a recording of action potentials and the transepithelial potential (TEP) of a trichoid sensillum with respect to the flight activity of the moth. The recording starts approximately 50 h after the beginning of the tip recording. The highpass-filtered signal (AC) reveals the action potentials superimposed on the slow fluctuations of the TEP, illustrating that there was no trend in the action potential activity. The time course of the TEP exhibited regular oscillations for periods of up to several hours, termed `oscillatory intervals'. These were interrupted by shorter periods, `non-oscillatory intervals', during which the TEP fluctuated less regularly or remained constant. Flight activity, recorded by a piezo-electric sensor at the thorax, was restricted to non-oscillatory intervals.