The distribution and morphology of various sensory organs (sensilla) on the antenna and mouthparts of Spodoptera littoralis larvae were investigated using scanning electron microscopy. In this study we focused on the morphological alterations of the antennal and mouthparts sensilla of Spodoptera littoralis last instar larvae reared on different host plants; alfalfa, cotton, and soybean leaves. Based on our results, we found that sensillum chaeticum on the antenna was morphologically affected by shifting the host plant since it became longer in those larvae reared on soybean and alfalfa leaves when compared with those reared on cotton leaves. Furthermore, several morphological variations were observed in sensilla trichodea on the labium, mandibles, and labrum by shifting the host plant. In addition, clear morphological changes were observed in sensillum digitiformium on the maxillary palps due to changing the host plant. On the other hand, no morphological changes in antennal basiconic, trichodium and styloconic galeal sensilla styloconica, maxillary campaniform and placodeum sensilla were observed. Taken together, these results showed that shifting host plants of Spodoptera littoralis larvae induced plasticity and morphological changes of the antennal and mouthparts sensilla.