Abstract: The fluctuating asymmetry (FA) in response to the stress of Bt-transgenic cotton was estimated among the different symmetric characters in the cotton bollworm (Helicoverpa armigera, CB) and the Asian lady beetle (Harmonia axyridis, ALB) populations in the laboratory. The CB was reared on transgenic Bt cotton and the ALB was reared on aphids (Aphis gossypii) feeding on transgenic Bt cotton. The results indicated that FA was found in fore femur, mid femur, hind femur, two vein sections L1 and L2 in fore wing and hind wing of the CB. The values of FA of fore femur and hind wing were higher than those of the control population. Egg hatchability and adult longevity of the CB were significantly lower than those of the control population. The fitness and predatory function of the ALB were not affected by feeding on aphids on transgenic Bt cotton. FA in hind wing of the ALB was not significantly different with the control population. The investigation showed some positive relationship between FA and fitness of CB and ALB, but more studies will be needed to establish the correlation between FA and fitness of these species. The possibility using FA as a sensitive indicator of the ecological risk of genetically modified crops was discussed.

Key words: Bt transgenic cotton, Helicoverpa armigera, Harmonia axyridis; fluctuating asymmetry, fitness