Increased atmospheric CO₂ concentrations may directly affect insect behavior. Thrips hawaiiensis Morgan and T. flavus Schrank are economically important thrips pests native to China. We studied the development, survival, and oviposition of these two thrips under elevated CO₂ concentrations (800 µl liter^–1) and ambient CO₂ (400 µl liter^–1; control) conditions. Both thrips species developed faster but had lower survival rates under elevated CO₂ levels compared with control conditions (developmental time: 13.25 days vs. 12.53 days in T. hawaiiensis, 12.18 days vs. 11.61 days in T. flavus; adult survival rate: 70.00% vs. 64.00% in T. hawaiiensis, 65.00% vs. 57.00% in T. flavus under control vs. 800 µl liter^–1 CO₂ conditions, respectively). The fecundity, net reproductive rate (R₀), and intrinsic rate of increase (r_m) of the two species were also lower under elevated CO₂ concentrations (fecundity: 47.96 vs. 35.44 in T. hawaiiensis, 36.68 vs. 27.88 in T. flavus; R₀: 19.83 vs. 13.62 in T. hawaiiensis, 14.02 vs. 9.86 in T. flavus; and r_m: 0.131 vs. 0.121 in T. hawaiiensis, 0.113 vs. 0.104 in T. flavus under control and 800 µl liter^–1 CO₂ conditions, respectively). T. hawaiiensis developed slower but had a higher survival rate, fecundity, R₀, and r_m compared with T. flavus at each CO₂ concentration. In summary, elevated CO₂ concentrations negatively affected T. hawaiiensis and T. flavus populations. In a world with higher CO₂ concentrations, T. hawaiiensis might be competitively superior to T. flavus where they co-occur.

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