The moths of the European corn borer, Ostrinia nubilalis (Hbn.), hemp borer, O. sp. aff. narynensis Mutuura et Munroe, and brushleg borer, O. scapulalis (Wlk.) were used in experiments. They were taken from both the natural and laboratory populations reared on the artificial medium (Gahukar, 1975). No valid postcopulative mechanisms, such as mor¬tality at the level of gametes and zygotes, sterility and mortality of hybrids, were found in our experiments. On the contrary, the hybrids obtained were normally developed, fertile and exhibited heterosis by some properties. At the same time the problem of ecological competence of hybrids in nature remains open, since the parental forms are characterized by distinct specialization for host plants. Since the crosses between these borers are con¬gruent, they appear to have similar chromosome sets.