AbstractWe have cloned and sequenced theCu, Zn superoxide dismutasegene ofChymomyza amoena. The coding sequence has the same length as inDrosophilaspecies and inCeratitis capitata. There are two introns, located at the same sites as inCeratitis. The second intron is absent inDrosophila: this placesChymomyzaoutside theDrosophilalineage, contrary to proposals based on anatomical and other evidence. The nucleotide or amino acid distances support a phylogeny in whichCeratitisfirst branches off the common stem, thenChymomyzasplits before the divergence of the two majorDrosophilasubgenera. The estimated divergence times are 58 million forChymomyza‐Drosophila; 48 million years for theDrosophilasubgenera. During the intervening 10 million years, theDrosophilalineage lost the second intron and evolved distinct codon‐preferences: the G + C use in the third coding positions is increased by 69% inDrosophilarelative toChymomyzaorCerati