Abstract: The morphological characteristics and inheritance of the melanic form of the oriental armyworm, Mythimna separata (Walker) that discovered in Beijing, China, was firstly reported in this article. Male and female adults of the melanic form were almost completely darkened in comparison with those of the typical form when they were reared under the same environmental conditions (temperature of 23±1℃ and photoperiod of L14∶D10). In the immature stages, the morphology of the melanic form was not basically different from that of the typical form. Larvae and pupae in the melanic form at the mass rearing condition and near emergence, however, were blacker in color than those of the normal form under the same environmental conditions. Genetic experiments showed that the inheritance of the melanic characteristics followed a Mendalian law, with the melanic allele recessive to the normal allele. Single pair of genes from the same chromosome regulated the melanic characteristics . These results indicated that the melanic form was the mutant of the typic al form, and both the melanic and typical form of the oriental armyworm still be longed to the same species although the melanic form had already become a new genotype. The significances of this finding to understanding the evolution of the oriental armyworm were discussed.

Key words: Mythimna separata, melanism, morphological characteristics, inheritance