Fig. 5. Sounds and body vibrations are produced by contractions of the remotor and promotor muscles. (A) Example of a simultaneous accelerometer recording of body vibrations and remotor and promotor muscle electromyograms (EMGs). The top photograph shows the anatomy of the two muscles (P, promotor; R, remotor). (B) Expanded view of a section of a different simultaneous recording of vibrations and muscle activity. There is a clear one-to-one relationship between each wave in the accelerometer recording (V), or carapace movement, and muscle activity. Scale: 10 mV for the top trace (vibration), 8 µV for the EMG traces; time scale=200 ms; B, top, 8 mV, 20 ms; bottom, 4 µV, 10 ms.