(a) Power spectra of unstimulated receiver vibrations in the DCX-EMAP mutant (blue traces in all panels), wild-type (grey traces) and f02655 excision controls (green). (b) Energy gain provided by active amplification deduced from the power spectra in (a)49. The range of wild-type values (one standard deviation around the mean) is marked in grey. Error bars display one standard deviation. (c) Response to pure-tone stimuli. Upper panel: Displacement response of the antennal receiver versus stimulus particle velocity. Lower panel: Mechanical sensitivity of the receiver plotted against particle velocity. Wild-type: grey, f02655 mutant: blue circles, f02655 excision control: green circles. (d) Response to force steps. Upper left panel: Displacement response of the receiver as a function of the stimulus force. Lower panel: The corresponding slope stiffness drops for small force amplitudes in wild type (grey) and excision controls, whereas it is constant for DCX-EMAP f02655 mutants (blue). The displacement-force relations of excision and control flies and the corresponding slope stiffnesses are well described by fits of a symmetric gating-spring model38. Right panel: CAP responses and predicted excess open probability versus receiver displacement. For wild type (grey) and excision controls (green), the mechanically evoked CAP response closely follows the excess open probability predicted from displacement data using a symmetric gating-spring model (solid lines for pO(×peak), dashed lines for pO(-×peak)7).