Abstract: The wasp Cotesia chilonis Munakata is one of the main larval parasitoids of the rice striped-stemborer, SSB, Chilo suppressalis(Walker). The behavioral responses of female Cotesia chilonis to volatile compounds emitted by these herbivores, rice or water-oat plants and herbivores damaged rice plants were studied with a Y-tube olfactometer. Female wasps were attracted to the volatiles from plants, stripedstemborer larvae and larval frass. Volatiles from herbivore damaged plants were more attractive to the female wasps than those from healthy plants. If larvae and larval frass were removed from damaged plants, these were no longer more attractive than mechanically damaged plants. However volatiles from herbivore damaged plants were also more attractive than healthy plants with larvae. This suggests that there is a synergy between volatiles from larvae damaged plants, larvae and/or larval frass. Rice plants that were damaged mechanically or/and treated with the larval regurgitant did not release attractive volatiles. The degree of attraction to volatiles from two varieties of seedlings, damaged plants, larvae fed on the two varieties of seedlings or their frass was not significantly different. These results indicate that the source of volatile compounds used by A. chilonis to locate its host habitat and host come from seedlings, larvae and larval frass, and more specifically, a combination of volatile compounds from plants, larva and/or frass.

Key words: Chilo suppressalis, Cotesia chilonis, rice seedling, water-oat seedling, volatile, behavioral responses