Аннотация:The unique and reiterated sequences of DNA of 7 species of Lepidoptera, cock-roach and a dragonfly were compared by means of molecular hybridization. Hybridization of 3H-labelled fraction of reiterated DNA sequences of Portetria dispar with the DNA of P. monacha showed 51% of homology, and with Bombyx mori DNA - 20% homology. Hybridization in permissive conditions revealed approximately twice as much homologies in the DNA compared. The three-fold increase in amount of nucleotide substitutions was observed. The thermostability of heteroduplexes correlates with homology levels. The fractions of unique DNA sequences of P. dispar is less homologous to DNA of other Lepidoptera species (13-46%). Interorder DNA hybridization of unique and reiterated fractions revealed 4-8% of homology.