Plant acids modulate chemosensory responses in Manduca sexta larvae

The effects of three plant acids on the gustatory response of Manduca sexta larvae were examined. Two different categories of response were recorded in the styloconic sensilla of different individuals in the presence of salt: the gustatory response to salt was reduced especially at the lower pHs; the deterrent cell fired particularly at the lower pHs. In some individuals neither response was seen except at the lowest pHs. Additional experiments indicated that the effect was due to pH and not to specific effects of any of the acids. Ascorbic acid was tested with the nutrient carbohydrates glucose and inositol, and was found consistently to reduce the gustatory responses to these compounds. The data indicate that plant acids at natural concentrations could influence food acceptability.