Abstract: Based on the systematical investigation of population dynamics of predacious ladybird in different cotton agroecosystem, the energy flow for predacious ladybirds was analyzed by the way of ecological energetic. The biological control efficiency of ladybirds was compared in different planting time and inter crop cotton agroecosystems using available date on the prepapers of ladybird ingestion to pest production. The results showed that the ingestion of predacious ladybirds were 26.45～70kJ·m^-2 yr^-1., accounting for 28.30～47.88% of all predacious natural enemies in different cotton agroecosystems. The biological control efficiency of ladybirds to aphids were 5.07～12.85%, which was decreased in inter crop cotton agroecosystems and the ecosystems with the delay of planting time. It is suggested that the ladybirds play the important role of potential biological control in cotton agroecosystems.

Key words: Predacious ladybird, Biological control efficiency, Function assessment, pre-incubation, forest soil., nitrogen transformation, soil cold storage, nitrogen content