Normalized frequency threshold curves of Amphipyra pyramidea L.
Stimulation with short tones was carried out at certain phases of a wingbeat cycle:
а - wings are at the upper point,
б - wings are situated horizontally and move up,
в  -  wings are situated horizontally and move down.

Horizontal axis represents a carrier frequency of a stimulus, kHz.
Vertical axis represents relative threshold levels.
SEM values are shown.