The effects of different levels of ascorbic acid, ascorbates and calcium carbonate on the texture of an alginate medium used for rearingSpodoptera littoralis Boisd.. were measured. Diet texture and ascorbic acid stability were found to depend on the Na/Ca ratio in favor of the calcium. The redox potential and vitamin C content of these diets were also examined, showing no significant correlation between these two parameters and age of the media.