Abstract: Celangulin V isolated from the root bark of the plant Celastrus angulatus is a new insecticidal compound. The effects of celangulin V on the midgut cells and digestive enzyme activities of Mythimna separata larvae were determined by means of electronmicroscopy and biochemical analysis. It was observed that the midgut cells and their organelles of poisoned larvae exhibited distinct pathological changes: the microvilli of the column cell were disordered and the number of microvilli was decreased markedly, thebasal infolding of the cell membrane was enlarged, in which the number of mitochondria was decreased. It was also observed that mitochondria had irregularly enlarged, the bilayer membrane was not intact, the cisternae of rough endoplasmic reticulum were distended; the cavity of goblet cell was enlarged, in which the microvilli came off. The results of biochemical analysis showed that the activities of protease, amylase and lipase of the poisoned larval midgut had no significant changes compared with the normal larval midgut. It is thus suggested that celangulin V might act on the plasmalemma and the organelle membrane of the midgut cells.

Key words: celangulin V, ultrastructure, digestive enzymes, Mythimna separata (Walker)