Food web of main arthorpods in 3 differently managed rice fields (low input, duck, apple snail farming) was investigated in Hongseong area, Chungcheongnam-do, Korea. Main arthropods were selected by their abundance during the rice growing season in 2010. Food web was analyzed with stable isotope, δ15N and δ13C according to rice growth satges (seedling, tillering, booting, blooming/heading, and ripening stage). Rates of δ15N and δ13C in soil (F=5.72; df=2, 6; P=0.0407, F=40.86; df=2, 6; P=0.0003, respectively) and δ13C in rice (F=6.46; df=2, 6; P=0.0319) were statistically different. Rate of δ13C in Lissorhoptrus oryzophilus (F=9.50; df=2, 6; P=0.0138), Pirata subpiraticus (F=11.00; df=2, 6; P=0.0098), and Pachygnatha clercki (F=6.33; df=2, 6; P=0.0333) were statistically different among farming methods. Stable isotope structures in food web were slightly different among 3 farming methods seasonally. Rates of δ15N and δ13C of rice pests such as Nephotettix cincticeps, Nilaparvata lugens, Laodelphax striatellus, and Sogatella furcifera were related to rice plant. Those of Tomoceridae sp. and Chironomidae sp., however, were not related to rice plant. Spiders as main natural enemy group were ranked on the top of food web and were thought to have life cycle based on the rice field from stable isotope structure.

• Seung Tae Kim(Research Institute for Agriculture and Life Sciences, Seoul National University)
• Sue Yeon Lee(Research Institute for Agriculture and Life Sciences, Seoul National University)
• Jong-Kook Jung(Entomology program, Department of Agricultural Biotechnology, Seoul National University)
• Joon-Ho Lee(Research Institute for Agriculture and Life Sciences, Seoul National University, Entomology program, Department of Agricultural Biotechnology, Seoul National University)