Abstract: Host age preference and effect of host age on development and reproduction of Anagrut nilaparvatae Pang & Wang, a mymarid egg parasltoid of planthoppers, were studied in the laboratory with constant temperature 23℃. This parasitoid showed no distinct Oviposition preference to eggs of different ages of the white-backed planchopper (WBPH)Sogatella furcifera(Horvath) as judged with the method of Manly (1972). However, as the age of host egg increased, its developmental period lengthened and the body size and fecundity of the issuing wasp decreased. The sex ratio and emergence rate of the offsprings were not affected by host age.For the adult the larger the body size, the higher the fecundity. This parasitoid obviously preferred eggs of brown planthopper (BPH) Nilaparvata lugenc(Stal) to that of WBPH when both were present. Body size and fecundity were greater in the issuing females from BPH eggs than in those from WBPH eggs. They developed slower in BPH eggs. The effect of different combinations of its original host and host eggs offered for nviposition were compared, and it was found that the female wasps which were raised fromWBPH eggs and offered with WBPH eggs (I.e. WBPH→WBPH) produced fewer progtny than other combinations (I.e. WBPH→BPH, BPH→WBPH and BPH→BPH). The intrinsic rate of increase (r_m) of this parasitoid with WBPH→WBPH was only 75% of that with other combinations. Assessment of host suitability for parasitoids by using suitability index (SI) is discussed.

Key words: Anagrus nilaparvatae——Sogatella furcifera, Nilaparvata lugens—— hest preference——host suitability index