Abstract: The bioassay data showed that the Asian corn borer ( Ostrinia furnacalis G. ) was unable to grow and develop on diet without sterols . When cholesterol or sitosterol was added to the diet withoutsterols, the larvae could normally grow and develop. They could also grow and develop on the stigmasterol diet, but the average body weight of 9-day larvae and pupation ratio were lower than that of the control and the cholesterol and sitosterol diet groups. The △⁷-lathosterol in diet was difficult to be metabolized in this species. After extraction and purification, the samples of sterols were analyzed by capillary GC. The results indicated that the quantity of cholesterol in 5th instar larvae of Asian corn borer fed on sitosterol diet was similar to that of the ones fed on normal diet, however the quantity of cholesterol in 5th instar larvae fed on stigmasterol diet was much lower. The results suggest that in Asian corn borer △⁵-plant sterols-sitosterol and stigmasterol could be converted to cholesterol by dealkylation at C₂₄ Of the side chain. But there exists metabolic difference between sitosterol and stigmasterol.

Key words: Asian corn borer, plant sterols, dealkylation