Abstract: 【Aim】 To reveal the biological characteristics of the red morph of the pea aphid, Acyrthosiphon pisum after feeding on Medicago staiva seedlings cultivated under different CO₂ concentrations, and to verify the population succession of this insect under elevated CO₂ concentration. 【Methods】 Red pea aphids were reared on M. staiva seedlings under three CO₂ concentrations ［380 (CK), 550 and 750 μL/L］ in CO₂ gradient chamber for six consecutive generations, and the growth parameters, reproductive parameters and population life parameters for each generation were observed and analyzed. 【Results】 The elevated CO₂ concentrations presented significant effects on the biological parameters of red pea aphids (P<0.05). With the increase of CO₂ concentration and the number of generations of the pea aphid, the developmental duration of red pea aphids was significantly prolonged, whereas the adult longevity was significantly shortened and the mean fecundity significantly decreased (P<0.05). Moreover, with the increase of CO₂ concentration, the net reproductive rate (R₀), intrinsic increase rate (r_m) and finite increase rate (λ)  of the same generation were all decreased, while the generation time (T) was shortened and then extended. The maximum net reproductive rate, intrinsic increase rate and finite increase rate in the pea aphid reared on M. staiva seedlings under 750 μL/L CO₂ concentration were decreased by 7.71%, 34.57% and 84.39% respectively, as compared with the control. 【Conclusion】 The elevated atmospheric CO₂ concentration presents negative effects on the population of the red morph of the pea aphid, which are more significant with the increase of generations.

Key words: Acyrthosiphon pisum, CO₂ concentration, alfalfa, life table, reproductive rate, population parameters