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ABSTRACT. The body angle and airspeed of free‐flying Drosophila hydei were measured and found to be inversely related. Values for the forces produced by a fly in level flight were calculated from the measured body angles, using published information from tethered fliers. The drag varied linearly with airspeed. The measured groundspeed of free fliers increased with starvation, not because of the change in weight and thus in the power‐to‐weight ratio, but through behavioural regulation of power output.
C. T. David (Fri,) studied this question.