Feeding and Oviposition Preferences and Demography of Rice Weevil (Coleoptera: Curculionidae) Reared on Mixtures of Brown, Polished, and Rough Rice

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In four mixed media composed of (1) brown and polished rice, Oryza sativa L., (2) brown and rough rice, (3) polished and rough rice, and (4) brown, polished, and rough rice, feeding and oviposition of the rice weevil, Sitophilus oryzae (L.), were observed. In all media, the weevil rarely exploited rough rice. The rice weevil fed on brown rice more frequently than on polished rice, but did not concentrate on brown rice in the media containing both brown and polished rice. The feeding preference index for brown rice over polished rice was ≍1.9. Females laid more eggs on brown rice than on polished rice. In the media containing both brown and polished rice, females laid eggs exclusively on brown rice; the preference index for brown rice over polished rice was ≍19.3. Mortality of the weevil during development in the medium without brown rice was significantly higher than in the media with brown rice. Life table statistics for the weevil in the four media showed that brown rice was the critical factor determining population development. Thus, the weevil's strong oviposition preference for brown rice allows it to maximize its fitness when feed with a variety of resources of different qualities. The relative impact of oviposition versus feeding preferences of the weevil on its reproductive success is discussed.