The southemgreen shield bug is a dangerous pest on rice and com crop. The adults show colour polymorphism. The density of the southern green shield bug is up to 13.7 individuals/m2 during reproduction of rice and 8.9 individuals/m2 at vegetative stage of com (7 - 9 leaves). Phenotype G has negative correlation with density on com and positive correlation with density on riqe, respectively. Phenotype 0 has positive correlation with density on com and positive .correlation with that on rice. Ten phenotypes of the southern green shield bug (G, O, F, OR, R, GO, OG, Y. B, C) were collected on maize and rice in Nghi Loc, Nghe An. To phenotype G belonged the largest number of individuals with 72.6 percent (N. viridula). Phenotype B, C were rare with only one female. The distribution of N. viridula's phenotypes on maize is different from that on rice. On maize 8 phenotypes were collected (excluding B and C) and 10 phenotypes on rice. Phenotype G, O, F are common on both maize and rice.