In the presentstudy, the effect of flufenoxuron on the sensory organ in the antenna of  Spodoptera littoralis was showed after feeding of the 3^rd larval instars for 24 hrs. on treated castor been leaves with Lc₅₀ . Each adult antenna, male and female of untreated and treated group is divided into about 77-82 segment like annuli; and each segment is divided into a sensory region containing the olfactory sensilla and a largely non-sensory region containing scales and a very small number of sensory structures.  Six types of sensilla were found on the antenna of adult S. littoralis: by scanning electron microscopy. These sensilla were trichoidae, chaetica, coeloconica, taste rod, sensilla auricillica and squamiforms. Two types of sexually dimorphic trichoidae were found; Type I is in the peripheral of the sensory field of the flagellar segments and present only on male antennae. This suggests that the sensillum may contain the receptor sites for the female sex pheromone. Type II is located within the ventromedial sensillar field of male and female where they are arranged without apparent pattern. Six mechanoreceptive sensilla chaetica on each segment of male and female were particularly abundant on the apical antennal segment. Each flagellar segment bears several sensilla coeloconica on the ventral surface of the antennae. Each sensillum consists of a depression surrounded by 15 to 17 teeth and one peg. There was a single sensillum taste rod on each segment. There is one of these sensilla at each segment in both male and female. On the terminal segment there were two sensilla joined. Sensilla auricillica were found on both male and female. These sensilla usually had a typical rabbit ear shape. The squamiform sensilla are found on both male and female on the dorsal part of the antenna among the scales. The study revealed that LC₅₀ of flufenoxuron caused the formation of abnormal antennae and effect the length and distribution of the sensilla.