Fig. 5. Flight efficiencies in Drosophila plotted against the number of open thoracic spiracles during flight. (A) Chemo-mechanical conversion—efficiency of the indirect flight muscles (IFM). (B) Aerodynamic efficiency is the ratio between Rankine–Froude power estimate for flight, , and the sum of induced and profile power (Ellington, 1984b). (C) Total flight efficiency is equal to the product between muscle efficiency and aerodynamic efficiency. Results are calculated using grey and red data shown in Figs 3 and 4. See text and legend of Fig. 3 for explanations. Values and means ± s.d. (N=10 flies).