Comparative study on the responses of maxillary sensilla styloconica of cotton bollwormHelicoverpa armigera and Oriental tobacco budwormH. assulta larvae to phytochemicals.

Using the electro-physiological technique, the sensory mechanisms of maxillary sensilla styloconica to stimulants and deterrents were explored on two closely related species, the generalistHelicoverpa armigera and the specialistH. assulta. The results showed that: (i) in both species, cells sensitive to sucrose and azadirachtin were mainly in the lateral sensillum styloconicum, and those to inositol were in the medial sensillum styloconicum; (ii) sensitivity of medial sensillum styloconicum inH. assulta to inositol was higher than that inH. armigera; (iii) among 6 tested deterrents, only azadirachtin evoked high impulse discharge from the lateral sensillum styloconicum in both insects; (iv) the deterrents could disturb stimulants evoking impulse discharge from maxillary sensilla styloconica of both species in different degrees: To sucrose evoking impulses on lateral sensillum styloconicum, forH. armigera capsaicin had a strong inhibition and gossypol had a weak inhibition, while forH. assulta tannic acid, gossypol, and tomatine all had strong inhibition except nicotine and capsaicin; to inositol evoking impulses on medial sensilum styloconicum, forH. armigera inhibition of tomatine was strong but that of gossypol was weak; and forH. assulta inhibition of gossypol was strong but that of nicotine was weak.