The AFM setup used to detect surface oscillations. (a) A special insect holder that restricts the motion of the insect. Laser light reflected from the AFM cantilever is
translated into the beetle’s vertical surface position. (b) An example of the recorded signal, and (c) its spectra; curve 1 is the signal coming from a live beetle, curve 2 is the
baseline signal recorded on a dead beetle. The room noise was recorded (curve ‘‘mic’’) with a wide-band microphone in the vicinity of the holder.