Inheritance of male courtship sound characteristics inDrosophila littoralis

Males ofDrosophila littoralis vibrate their wings during courtship to deliver a love song. This consists of 25- to 50-ms-long pulses with a basic frequency of about 250–400 Hz, separated by 250- to 500-ms pauses. When recording the sounds of flies from several localities in Europe, we found that males of one strain from northern Finland displayed courtship sounds with an unusally low wing beat frequency (below 250 Hz). In a genetic analysis utilizing marker stocks, the anomalous frequency was found to be caused by genes on all major autosomes, the strongest factors being on the second chromosome. Interaction between genes on chromosome 2 and on the fused chromosome 3–4 was nonadditive. In low-frequency sounds, the number of cycles in the pulse (CN) was decreased, so that the length of the sound pulse (PL) remained more or less unchanged. We suggest that the genetically and physiologically most thoroughly controlled trait in the sound ofDrosophila littoralis is the length of the pulse.