Ontogenetic manifestations of four isozymes namely, acid phosphatase, alkaline phosphatase, α-esterase and β-esterase have been analysed in two closely related species—D. nasuta nasuta andD. sulfurigaster neonasuta. By adopting polyacrylamide gel electrophoretic technique 15 different developmental stages have been assayed. Electrophoretically homologous and distinct enzyme phenotypes for each enzyme system have been recognised in the two species under study. The implications of these findings are discussed.