Intra- and inters-specific effects of Nilaparvata lugnes (St l) and Sogtella furcifera (Horv th)(Homoptera: Delphacidae) on their population performances on Indica Zhe 852, Japonica XiuShui 11 and Hybrid XY 9308 were studied in the laboratory. Intra-specific crowding did not influence the performance of N. lugens except for emergence rate on Z 852, but adversely affected the nymphal development duration of X. furcifera on Xiushui 11 and XY 9308, and emergence rates, adult longevity and fecundity on Xiushui 11. The inter-specific interactions between the nymphs of N. lugens and S. furcifera provided positive effects for both the species, but more benefits to S. furcifera.The nymphal development duration, emergence rate and fecundity of S. furcifera raised in mixed cultures for all the three varieties were often significantly shorter or higher than those raised in pure cultures, but only the emergence rate and fecundity of N. lugens raised in mixed cultures. on Zhe 852 and XY9308 were higher than those raised in pure culture. Both species suffered little delayed negative intra-specific effects and gained dramatic delayed positive inter-specific effects from another species previously fed on the plants. The nymphal development duration, adult emergence rate, female longevity and fecundity of each species were positively affected when reared on the plants sucked by another species before. The change of distribution pattern of S. furcifera reared on the plants fed by BPH before revealed the positive effects from inter-specific.