Journal of Environmental Sciences 19(2007) 1318–1325 Response of successive three generations of cotton bollworm, Helicoverpa armigera (H¨ ubner), fed on cotton bolls under elevated CO 2 WU Gang 1,2 , CHEN Fa-jun 1 , SUN Yu-cheng 1 , GE Feng 1, ∗ 1. National Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China. E-mail: wugang@ioz.ac.cn 2. Department of Biology, Wuhan University of Technology, Wuhan 430070, China Received 18 October 2006; revised 3 November 2006; accepted 22 March 2007 Abstract The growth, development and consumption of successive three generations of cotton bollworm, Helicoverpa armigera (H¨ ubner), fed on cotton bolls grown under elevated CO 2 (double-ambient vs. ambient) in open-top chambers were examined. Significant decreases in protein, total amino acid, water and nitrogen content and increases in free fatty acid were observed in cotton bolls. Changes in quality of cotton bolls affected the growth, development and food utilization of H. armigera. Significantly longer larval development duration in three successive generations and lower pupal weight of the second and third generations were observed in cotton bollworm fed on cotton bolls grown under elevated CO 2 . Significantly lower fecundity was also found in successive three generations of H. armigera fed on cotton bolls grown under elevated CO 2 . The consumption per larva occurred significant increase in successive three generations and frass per larva were also significantly increased during the second and third generations under elevated CO 2 . Significantly lower relative growth rate, efficiency of conversion of ingested food and significant higher relative consumption rate in successive three generations were observed in cotton bollworm fed on cotton bolls grown under elevated CO 2 . Significantly lower potential female fecundity, larval numbers and population consumption were found in the second and third generations of cotton bollworm fed on cotton bolls grown under elevated CO 2 . The integrative effect of higher larval mortality rate and lower adult fecundity resulted in significant decreases in potential population consumption in the latter two generations. The results show that elevated CO 2 adversely affects cotton bolls quality, which indicates the potential population dynamics and potential population consumption of cotton bollworm will alleviate the harm to the plants in the future rising CO 2 atmosphere. Key words: elevated CO 2 ; Helicoverpa armigera; growth; development; fecundity; cotton bolls; population consumption; successive generation Introduction Global atmospheric CO 2 concentration is currently in- creasing at a rate of approximately 1.5 μl/(L·a) largely owing to combustion of fossil fuels and the clearing of forests, especially in the tropics, and is expected to double within 21st century from its current level of 360 to 700 μl/L (Goverde et al., 1999; Wigley and Raper, 1992; Rossi et al., 2004). Profound impacts of elevated CO 2 on terrestrial ecosys- tem (Dong et al., 2006; Yu et al., 2006), especially on chemical composition and nutrient quality of plants, are expected (Luo et al., 1999; Penuelas et al., 2002), that is, significant increases in photosynthesis, growth, water use efficiency, leaf area, yield and decreases in foliar nitrogen of plants, particularly C 3 plants, (Oechel and Strain, 1985; Project supported by the National Basic Research Program (973) of China (No. 2006CB102002); the Pilot Project of Knowledge Innovation Program of Chinese Academy of Sciences (No. KSCX2-YW-N-006) and the National Natural Science Foundation of China (No. 30571253, 30621003). *Corresponding author. E-mail: gef@ioz.ac.cn. Cure and Aycock, 1986; Bazzaz, 1990; Prtchard et al., 1999; Oijen et al., 1999). As nitrogen is an important limiting factor for phytophagous insects (Mattson, 1980), and reduction in percent nitrogen alone may have po- tential effects on insect performance. Most leaf-chewing insects exhibit compensatory increases in food consump- tion and/or reduced growth, survival rates, and reduction in density, presumably due to increasing foliar C:N ratio (Scriber, 1982; Masters et al., 1998). For example, red- headed pine sawfly larvae increase nitrogen utilization efficiency in response to CO 2 -mediated declines in foliar nitrogen in loblolly pine (Williams et al., 1994). Higher rates of insect mortality have been associated with nutri- tional deficiency that results from reduced foliar nitrogen concentrations under elevated CO 2 (Brooks and Whittaker, 1999; Stiling et al., 1999). Lincoln (1986) and Osbrink et al. (1987) reported that leaf-chewing insect herbivores exhibited compensatory increases in foliar consumption rate or a delay in development when reared on plants grown in elevated CO 2 environments. There are few studies to measure the direct effects of