Figure 4.

Sawtooth oscillator. Upper trace of horizontal black bars represents timeline of a focal animal (foc) broadcasting periodic signals of length x. Lower trace of horizontal blue bars indicates timeline of a stimulus (stim) or neighbour's signal of length y. The focal animal's central oscillator, sawtooth red line, ascends to its peak level and triggers a signal that is broadcast after a brief effector delay t. The oscillator returns to its basal level over an interval r; it is immediately reset to its basal level when a stimulus is perceived, and it remains inhibited at basal level until the stimulus ends. Ascent following inhibition is faster than during solo signalling. The focal animal's free-running period is T; a stimulus perceived during oscillator ascent (positive d, event 1) lengthens the concurrent period (T'), a temporary phase delay, while a stimulus during oscillator return (negative d, event 2) shortens the next period, a temporary phase advance. Once triggered by the oscillator, a signal is invariably broadcast. Open black bars indicate when the focal animal would have signalled were the stimulus absent. Timelines are all referenced to absolute time. Model developed from tests with fireflies [12,13] and acoustic insects [14].