Neope goschkevitschii and N. niphonica are closely related species that occur sympatrically in various areas of Japan. In order to verify the possible existence of natural hybrids and genetic introgression between these species, artificial hybridization and backcrossing experiments were conducted by hand pairing. The results showed that adult male and female F1 hybrid individuals of both species were not capable of reproducing and that genetic introgression between these species must not occur in the natural environment.