Oscilloscopic and stroboscopic analysis of the flight sounds of Drosophila.

1. Oscillographic records are presented of the sounds produced by Drosophila funebris during "fixed" flight. Stroboscopic determinations of wingbeat frequency indicate that one cycle of wing motion corresponds to one cycle of flight sound.2. The sounds generated during flight are complex and radically different from the simple harmonic motion of a tuning fork. Certain consequences of this fact are discussed.3. Analysis of these sounds suggests a remarkable aerodynamic efficiency for the wingbeat cycle. The flying insect produces a polarized flow of air from front to rear during approximately 85 per cent of the wingbeat cycle.4. During brief periods of flight the first few and the last few beats of the wings are accomplished at the high frequency characteristic of the entire flight. This fact is considered in relation to Pringle's new observations concerning the neuromuscular system of dipterous insects.