Do the song pulses of Drosophila show cyclic fluctuations?

Following analysis of the song of two Drosophila species, Kyriacou and Hall in 1980 described a rhythmic variation in the intervals between sound pulses. This rhythmicity was species specific and various mutants also showed characteristic song-period rhythmicity. Recent attempts by Ewing and by Crossley to confirm the existence of the rhythms, using essentially similar methods, have failed; Kyriacou and Hall have since ascribed these failures to differences in technique and methods of measurement between them and their critics, and re-affirm that the rhythmicity they described exists. In view of the controversy surrounding the existence of song-period rhythmicity, a body of work on the genetics of this behaviour must be viewed with caution.