MUSCLE EFFICIENCY AND ELASTIC STORAGE IN THE FLIGHT MOTOR OF DROSOPHILA

Insects could minimize the high energetic costs of flight in two ways: by employing high-efficiency muscles and by using elastic elements wi thin the thorax to recover energy expended accelerating the wings. How ever, because muscle efficiency and elastic storage have proven diffic ult variables to measure, it is not known which of these strategies is actually used. By comparison of mechanical power measurements based o n gas exchange with simultaneously measured flight kinematics in Droso phila, a method was developed for determining both the mechanical effi ciency and the minimum degree of elastic storage within the flight mot or. Muscle efficiency values of 10 percent suggest that insects may mi nimize energy use in flight by employing an elastic flight motor rathe r than by using extraordinarily efficient muscles. Further, because of the trade-off between inertial and aerodynamic power throughout the w ing stroke, an elastic storage capacity as low as 10 percent may be en ough to minimize the energetic costs of flight.