A bioassay was developed to assess the in vitro feeding responses of Chilo partellus larvae to susceptible (Inbred A) and resistant (MP 704) maize varieties. Consumption of internode tissues from the two maize varieties differed while the reverse was true for the nodes. Aqueous extracts from the two varieties caused a decrease in feeding and weight gain, but these effects were more evident in MP 704 than in Inbred A treatments. This suggests that MP 704 has a water extractable factor affecting weight gain negatively. Dose-response curves of neural responses from the maxillary styloconica sensilla showed that aqueous extracts from the two maize varieties evoked different functional forms of impulse frequencies especially in the lateral sensilla. These observations suggest that the quality of gustatory stimuli in the two maize varieties differs.
