Elevated CO2 lessens predation of Chrysopa sinica on Aphis gossypii

Most studies on the effects of elevated atmospheric CO2 on organisms have focused on the performance of plants or herbivores. Few reports have examined the impact on the ability of predators at the third trophic level. In this experiment, we made use of open-top chambers to quantify the effects of elevated CO2 on growth, development, and predatory ability of two successive generations of Chinese lacewing, Chrysopa sinica (Tjeder) (Neuroptera: Chrysopidae), feeding on cotton aphids, Aphis gossypii (Glover) (Hemiptera: Aphididae), which were reared on cotton, Gossypium hirsutum L. (Malvaceae), grown under elevated CO2 (double ambient vs. ambient). Higher atmospheric CO2 concentrations reduced the duration of larval development and the survival rate of pupae, and caused decreased weight in adult female C. sinica, but had no significant effects on survival rate of each larval stage, female adult fecundity, egg hatch rate, or adult life span. The predatory ability of larvae in the third instar and the total larval stage of C. sinica that fed on A. gossypii were significantly lower in elevated CO2 environments. The number of aphids consumed by first-generation lacewing population did not change significantly with different CO2 treatments; however, significantly fewer aphids were consumed by the second generation of the lacewing population with elevated CO2. We speculate that A. gossypii may become a more serious pest under an environment with elevated CO2 concentrations because of the reduced predatory ability of C. sinica on A. gossypii.