Abstract: Environmental scanning electron microscopy and biochemical techniques were employed to analyze the structure of the normal and fluorescent brightener 28(M2R) treated peritrophic membrane(PM) of Spodoptera exigua. The normal PM surface was smooth and wrinkled without pores or slits while the treated PM surface had pores and slits.There were many types of protein in the PM. SDS-PAGE separation of the PM suggest that there are at least 17 polypetides,most of them less than 97.4kD. Proteins formed 41.98% of the total mass of the PM and carbohydrates 2.05%. The PM proteins could be dissociated from the PM in vitro by M2R. Droplet feeding fifth instar larvae with M2R greatly increased the permeability of the PM.

Key words: Spodoptera exigua, peritrophic membrane, fluorescent brightener, environmental scanning electron microscopy