Strains of Drosophila ananassae from various places in the Tropics were investigated for their electrophoretical amylase pattern. Eleven isoamylases were found in adult flies. African populations were much more polymorphic than those from the Far East, and showed multibanded phenotypes, suggesting a multiplication of the Amy structural gene, with at least four copies per haploid genome in certain populations. Nine other species of the D. ananassae subgroup had weak amylase activity and only one or two variants were found in each species. D. monieri and D. varians are closely related to D. ananassae and showed a single band, similar to the isoamylase 3 of D. ananassae, which suggests that this might be an ancestral allele.