Composition, Structure and Dynamics of Arthropod Communities in a Rice Agro-Ecosystem

The study on terrestrial arthropod communities in rice agro-ecosystems was conducted in Bathalagoda, Sri Lanka. A total of 342 arthropod species was documented comprising 282 species of insects in 90 families and 17 orders and 60 species of arachnids in 14 families. Eight taxa new to Sri Lanka are reported. Majority of the insects documented were hymenopterans, dominated by bees and ants. Based on feeding habits, majority of the arthropods recorded were predators (149 species), dominated by spiders. However, in the rice field proper, abundance of phytophagous rice pests was higher than that of predators. Density fluctuations of predators and parasitoids were positively correlated. Species richness and diversity of terrestrial arthropods increased gradually with crop age, but declined following application of pesticides. Species diversity (H') of terrestrial arthropods during vegetative, reproductive and grain ripening stages and the fallow period were significantly different. Diversity of terrestrial arthropods in the field proper positively correlated with crop age and height of the rice plant, and in field bunds with the weed cover. Findings indicate that a stable relationship could be maintained between rice insect pests and their arthropod natural enemies through minimal biocide applications and manipulation of weed cover in the rice agroecosystem. Key Words: Rice fields, arthropods, diversity, species richness, pests, natural enemies doi: 10.4038/cjsbs.v37i1.494 Cey. J. Sci. (Bio. Sci.) 37 (1): 23-48, 2008