Genetic variation in larvae and imagines of three species of Heptageniidae from central Italy,Ecdyonurussp.(venosusgroup),Elec‐trogena grandiae(Belfiore, 1981), andElectrogena lateralis(Curtis, 1834) was studied by starch‐gel electrophoresis. Thirteen enzyme systems were analysed for a total of 20 loci (Aat, Ada, Adk‐1, Adk‐2, Ck‐1, Ck‐2, Est‐1, Est‐2, α‐Gpdh, Gpi, La‐1, La‐2, Mdh‐1, Mdh‐2, Me‐1, Me‐2, Mpi, Pap, Pgm‐1, Pgm‐2), 15 of which were expressed in adults and 16 in the larvae. Only 11 loci (Aat, Ada, Est‐2, Gpi, La‐2, Mdh‐1, Me‐2, Mpi, Pap, Pgm‐1, Pgm‐2) were shared by larvae and adults. Observed heterozygosities were always lower than expected values; higher values were observed in larvae than in adults. Fixation indices and genetic distances were higher in the adults; however, the two genera were better discriminated using the larval samples. In conclusion, comparisons using larvae and adults simultaneously should be avoided, and absolute values of genetic identities and genetic distances to assess systematic levels have to be considered with caution, since they can vary from one developmental stage to another.