Abstract: Consecutive cotton-barley intercropping is a common practice in Jiangsu Province, where barley is interplanted in cotton fields in the autumn, and cotton is interplanted in barley in the following summer. Field studies during 1987-1988 in Yancheng, Jiangsu Province showed that harvesting of the crops and the cultivation practices pre- and after harvest were the major factors causing fluctuations of the natural enemy populations. Removal of the harvested barley in summer carried away a great number of parasites and predators. Also, dispersal and high mortality of predators occurred in the autumn after harvest of cotton plants. It was demonstrated that planting cotton in the barley fields in an earlier season or leaving the harvested plants in the field for a certain length of time would allow the natural enemies to transfer on to the interplanted cotton plants. Planting ground cover crops or green manure in the cotton fields protected the overwintering predators and significantly increased their population numbers in the following year.