QUANTIFYING PREDATION BY UMMELIATA INSEC‐TICEPS BOES. ET STR. (ARANEAE: LINYPHIIDAE) ON RICE PLANTHOPPERS USING ELISA*

Abstract

Abstract An enzyme‐linked immunosorbent assay (ELISA) has been developed to quantify predation by Ummeliata insecticeps Boes. et Str. on rice planthoppers in paddy fields in Dasha Township, Guangdong Province. The assay was completely specific for rice planthopper materials. The detection periods for antigens after an adult of U. insecticeps had fed on three 3–5th instar nymphs of white‐back planthopper (WBPH), Sogatella furcifera (Horvath), and brown planthopper (BPH), Nilaparvata lugens (Stal), at room temperature were 96 h and 120 h, respectively. The proportion of individual species of predators scoring positive ranged from 19. 05% to 47. 34% for WBPH, and from 9. 25% to 66. 67% for BPH in the early rice season. Although the numbers of the rice planthoppers consumed by U. insecticeps increased with increasing prey densities, the predation rates declined. When rice planthopper densities were low, the predation rates were relatively high. This kind of predation can explain why the rice planthoppers have never reached outbreak levels in rice fields in Dasha Township since 1973.