Fig. 5. Effects of wingbeat amplitude on mean intratracheal pressure during flight in Manduca sexta. (A) At the anterior spiracles (spiracles I), the wingbeat amplitude maxima coincide with the pressure minima. (B) At the mesoscutellar air sac, the wingbeat amplitude maxima coincide with the pressure maxima. Recording techniques are as described in the legend to Fig.4. Voltage values for wingbeat curves have been converted into angular degrees of wing position from 0° (no flight) to 110° (with maximum angle corresponding to maximum wing-stroke amplitude during steady flight).