WING BEAT FREQUENCIES IN DROSOPHILA-MELANOGASTER SELECTED FOR DIFFERENT WING LENGTHS

Wing beat frequencies (w.b.f.) and plasticity of w.b.f. were investiga ted in Drosophila melanogaster lines selected for Long and Short wings at two different temperatures. Flies were glued with their thorax to a thin thread and wing beat frequency was determined by use of a strob oscope. Flights were performed at two different ambient or Flight temp eratures. Wing length and wing area were measured afterwards. Wing bea t frequency increased with increasing temperature except in the Long l ine selected at 20 degrees C: most lines showed phenotypic plasticity in w.b.f. In the lines selected at 25 degrees C the Short line had a s ignificantly higher w.b.f. than the Control and Long line at both Flig ht temperatures. The genetic differences in w.b.f. between the lines r emained constant. Lines selected at 20 degrees C showed no differences in w.b.f. at both Flight temperatures. Significant Genotype-by-Enviro nment interactions were observed. Various hypotheses are posed for the adaptive significance of changes in w.b.f. due to temperature, in ter ms of wing load, flight muscles and optimal flight temperatures.