Variations at three flight-related enzyme loci, delta-glycerophosphate dehydrogenase (delta-Gpdh), glucose-6-phosphate dehydrogenase (G6pd), and phosphoglucomutase (Pgm), of Epiphyas postvittana (Walker) moths were investigated using starch gel electrophoresis. Among the three enzyme loci, delta-Gpdh and G6pd were found to be monomorphic, but Pgm was polymorphic, with a total of seven different genotypes and five alleles identified in this study. Comparisons of allozyme variability at the Pgm locus showed significant differentiation among five natural populations sampled from geographically distinct localities in New Zealand and Australia and between laboratory populations differentiated by artificial selection on flight capacity. The Pgm polymorphism was shown to be associated with the variation of flight capacity, but the role of the enzyme locus in the evolution of flight behavior is to be demonstrated in this species.