[Dynamics of predatory natural enemy community in cotton fields]

The dynamics of predatory natural enemy community in cotton field along the Yangtze River in Anhu province was studied. The results showed that there were totally 19 species of predatory natural enemies, and the dominant species were Propylaea japonica, Erigonidium graminicola, Theridium octomaculatum, Misumenops tricuspidatus, Orius minutes and Geocoris ochropterus. The predatory natural enemies in the cotton fields were rather abundant in the whole growing period of cotton, except the rainy season. Among the dominant species, P. japonica, M. tricuspidatus, O. minutes and G. ochropterus were distributed mainly in the upper and middle parts of cotton plants, while E. graminicola and T. octomaculatum mainly in the middle and lower parts of cotton plants. The diversities of the community were relatively high in the early developmental period of cotton, and reached the top level in the bud and flowering period of cotton in the first 10 days of July, then declined successively hereafter. The principal factor affecting the diversity was species richness in the early developmental period of cotton (from shoot period to bud and flowering period), and species evenness in the late developmental period of cotton (from flowering and boll period to boll opening period). The characteristics of the community were relatively analogous before the second 10 days of August (from shoot period to flowering and boll period of cotton), but after this period, the characteristics changed obviously with the features of the dominant species getting more and more conspicuous.