Abstract: The population dynamics of insect pests and their natural enemies in single and intercropped cotton field ecosystems are analyzed, and the controlling effects of natural enemies in these ecosystems are compared. The results show that the population densities of cotton seedling aphids (Aphis gossypii) and 2nd generation cotton bollworm (Helicoverpa armigeria) are lower in intercropped than in single cotton field ecosystem, but those of summer aphids and 3rd generation cotton bollworms as well as the energy production of natural enemies (especially that of predacious spiders) are converse. From the viewpoint of function, the preservation effect on natural enemies is greater in intercropped than in single cotton field ecosystem, but the controlling effect of natural enemies on insect pests is converse.

Key words: Cotton field ecosystem, Diversity, Natural enemy, Insect pest, quantification, heavy metal, coastal waters of China, sediment, source apportionment