The Wing Mechanism Involved in the Courtship of Drosophila

Many species of Drosophila have courtship displays in which the male vibrates one or both wings after approaching the female. In Drosophila melanogaster the major part of this display occurs with the wing nearer the female extended to nearly 90 from the long axis, in which position the wing is vibrated (Spieth, 1952). It has been shown that this vibration is accompanied by a train of sound pulses (Shorey, 1962) and that such sound pulses provide stimuli which render the females sexually receptive (BennetClark & Ewing, 1967). Several different species of Drosophila have been studied and we have shown that many of these have a characteristic courtship song (Ewing & Bennet-Clark, 1968) where there is, within any species, close control over the interval between sound pulses, the frequency of the sound within the pulse and the duration of each pulse. The simplest song, acoustically, is a train of single cycles of pressure change each of 3 msec, duration produced at 34 msec, intervals by Drosophila melanogaster. D. persimilis produces trains of 3-7 cycles of a frequency of 525 cyc./sec. at 55 msec, intervals. D. bipectinata produces single cycles of 2 msec, duration, repeated at 8-4 msec, intervals. In each species the wings can be seen to vibrate while this sound is produced (Ewing & Bennet-Clark, 1968). This paper describes the probable nature of the aerodynamic events causing these sounds and examines the wing mechanism involved, relating this to normal flight and flight initiation in Drosophila and other Diptera.