Electrophysiological tests were done on larval and adult stages of Chilo partellus. The first tarsomere on the forelegs of the moths has three pairs of sensilla; two of them have similar ultrastructural details and they are innervated by gustatory cells which respond equally well to maize leaf exudate but differ in their sensitivity to sucrose. Although the third pair has morphological features resembling those of contact chemoreceptor, it responds to mechanical stimulation only. Taste sensilla on the ovipositor are more sensitive to NaCl than sucrose and they respond to the unknown components in the maize leaf exudate. On the larval maxillae the lateral styloconica sensilla are very sensitive to sucrose and the aqueous extracts from susceptible and resistant maize cultivars; the medial styloconica sensilla are mainly sensitive to NaCl and the aqueous exudate from maize stems. Preliminary tests showed that treated maize piths can provide a suitable medium for the bioassay of larval feeding behaviour.

Eleetrophysiological recordings from taste sensilla of larvae of Chilo partellus (Swinhoe), Eldana saccharina Wlk. and Maruca testulalis (Geyer) during stimulation with various plant substances revealed that in the medial and lateral maxillary sensilla styloconica of each of these three species a NaCl, water and sucrose sensitive cell is present. In the medial styloconic sensilla of C. partellus, an additional chlorogenic acid sensitive cell occurs. Chilo partellus and E. saccharina appeared to be more sensitive to sucrose than M. testulalis. In all three species, the lateral sensilla styloconica are more responsive to sucrose and less responsive to NaCl than the medial ones.