The dual-choices tests of behavioral test were used to study the gustatory behavioral responses to caffeine of Helicoverpa armigera larvae and H. assulta larvae. Electrophysiological responses were studied by electrophysiological tip recording. Behavioral experiments showed that caffeine was a feeding deterrent for both larvae,but it showed a stronger feeding deterring effect on the oligophagous H. assulta. The electrophysiological tip-recording results showed that both H. armigera larvae and H. assulta larvae had one caffeine-sensitive feeding deterrent neuron at the medial sensilla,and the electrophysiological pulse response of H. assulta larvae was significantly stronger than that of H. armigera larvae. Therefore,caffeine had a stronger feeding deterring effect on the oligophagous H. assulta than the polyphagous H. armigera. The difference in behavioral effect was closely related to the sensitivity of to caffeine the feeding deterrent neurons at the medial sensilla.
Dual-choice behavioral assays and electrophysiological tip-recording technique were used to investigate the taste adaptation of different diet-experienced fifth instar larvae of Helicoverpa armigera to azadirachtin. The behavior test showed that the larvae reared with normal artificial diets were highly deterred by azadirachtin. However,the larvae reared with the artificial diets containing low concentration of azadirachtin showed insensitivity to azadirachtin. The electrophysiological tests showed that there was a changed responsiveness in the deterrent neuron responding to azadirachtin in the lateral sensilla styloconica of different diet-experienced larvae. It indicated that there was a taste adaptation to azadirachtin in different diet-experienced larvae of H. armigera and this taste adaptation was correlated with desensitization of related taste neurons.
