Gypsy moth larvae, Lymantria dispar (L.), are polyphagous feeders. The medial styloconic sensillum of this species bears a taste receptor cell that responds to alkaloids and another that responds to the sugar alcohol, inositol. The lateral styloconic sensillum bears a taste receptor cell that is sensitive to the sugar, sucrose. We tested the effect of two phagostimulants, namely sucrose and inositol, on the response of the deterrent-sensitive cell and found that both phagostimulants suppressed its response, equally, while their combination was significantly more effective. We also tested the effect of two alkaloids (i.e., strychnine and caffeine), which deter feeding in this species, on the response of the inositol- and sucrose-sensitive cells. Although both of these deterrents had no effect in suppressing the response of the sucrose-sensitive cell, they both had an effect in suppressing the inositol-sensitive cell. We also found that sucrose suppressed the response of the inositol-sensitive cell, whereas inositol had no significant effect on the response of the sucrose-sensitive cell. In this paper, we examined the effect of mixtures of these compounds to determine the nature of their interaction. In the context of host–plant interactions and, for example, host recognition, whereby host plant acceptability depends on the total sensory impression acquired from responses to multiple plant components rather than the presence or absence of single stimulant or deterrent compounds, this study could have a direct bearing in the development of natural compounds (i.e., alkaloids) for pest control and crop protection. It will also contribute to our understanding of the neural basis of the feeding behavior of this insect.