Fig. 7. Body pressure changes in response to adduction and retraction. (A) Pressure changes were measured at the base of the subcoxa in segment A4 (upper trace) while monitoring the separation of the prolegs in all body segments (lower traces). An upward deflection indicates an increase in pressure and retraction of the prolegs. Proleg movements tend to occur concurrently in different body segments. The pressure scale bar corresponds to 980 Pa (10 cmH₂O). (B) The first 9 s of data for the pressure and prolegs in A5 are shown on an expanded scale. The magnitude of the pressure trace has been rescaled to demonstrate the close relationship between pressure changes and proleg movements. (C) A cross-correlation plot of movements and pressure change in A5. A peak at the dotted line would indicate exact coincidence of movement and pressure. Here, the peak lags behind, showing that the pressure pulse precedes the proleg movement by 200 ms. This correlation is very similar for the other prolegs at the start of the recording but the relationship breaks down completely for the rest of the recording (see text).