Histograms of interpulse intervals between the acoustic clicks (noctuid moths Amphipyra perflua F.):
a - moths in partially restricted flight (10 tests, a total of 1800 intervals);
b, c - spontaneous activity of 2 specimens in tethered flight. Arrows mark the points at the time axis corresponding to the single wing-beat period (T is nearly 29 ms).
The b-histogram results from the accumulation of 500 clicks sequence, the c-histogram - that of 100 clicks. Discretization step is 2 ms.