Abstract: Laboratory experiments were conducted to study the role of infochemicals from rice volatiles and rice planthoppers, and morphological characters of rice planthopper eggs, in host discrimination by the egg parasitoid, Anagrus nilaparvatae, between the brown rice planthopper (BPH), Nilaparvata lugens (Stal), and the whitebacked rice planthopper (WBPH), Sogatella furcifera (Horváth). The results indicated that there was no significant difference in attractiveness between BPH femaleinduced rice volatiles and WBPH female-induced rice volatiles, each of which attracted 57.50% (23) and 42.50% (17) of parasitoids tested, respectively. In a comparison of 4 types of BPH and WBPH materials, i.e., intact eggs, mashed eggs, plants with eggs and nymph-damaged plants, parasitoids showed no preference for any material except intact eggs, spending longer time on BPH eggs than on WBPH eggs. The headspace composition of BPH-infected rice plants was similar to that of WBPH-infected rice plants. The results suggest that infochemicals, kairomone from hosts and synomone from host-infected rice volatiles, and the morphological characters of eggs, do not mediate discrimination by the parasitoid between BPH and WBPH. The mechanism of host discrimination by the parasitoid between BPH and WBPH is discussed.

Key words: Nilaparvata lugens, Sogatella furcifera, Anagrus nilaparvatae, infochemicals