Abstract: In this research try to explore the effect of injection and forced ingestion of Cestrum CSE on two insect species: Schistocerca gregaria and Spodoptera littorais. A fat body necrosis (for Spodoptera larvae) and a digestive tract softness (for Schistcerca larvae) are observed, this let us to make an histological study of these organs. Theses studies reveals a cytotoxic effect of CSE on the fat body of Spodoptera larvae, the cells of this tissue decreases in size and becomes more colored probably by loss of their cytoplasmic cotenant. More over we have noted a cell destruction of the foregut and of the gastric caeca of Schistocerca treated with CSE forced ingestion. Our hypothesis is that saponins interact with membrane cholesterol, this causes a membrane destabilization and that provokes cell death.