The cotton aphid, Aphis gossypii, is a worldwide and polyphagous pest. The host plants are more than 300 species in various botanical families. The adaptations of this aphid to various host plants are different, but so far, the special host\|biotypes of cotton aphid have not been identified. In this paper, the selectivity of cotton aphid to different host plants, the survival rate, reproduction capability and feeding behavior of the aphid after host transformation are studied by directional selection, h...