The composition of artificial diet for the rice stem borer, Chilo suppressalis (Walker), was further optimized by the second orthogonal design trial with 5 factors and 4 levels. The composition of the artificial diet was as follows: rice stem flour 18.75 g, soybean 15.00 g, wheat germ flour 15.00 g, rice chaff flour 6.25 g, wateroat flour 7.50 g, casein 10.00 g, yeast flour 18.75 g, cellulose 7.50 g, sucrose 15.00 g, glucose 7.50 g, vitamin C7.50 g, vitamin B 3.00 g, cholesterol 0.375 g, chlorination 0.25 g, Beck mix salt 2.50 g, Sorbic acid 1.35 g, Agar 13.49 g and tap water 809.25g. Evaluation of the optimized diet was carried out by comparison with the natural food, fresh rice stem, by rearing the rice stem borer for continuous three generations. It was concluded that the optimized artificial diet was better than the fresh rice stem evidently as far as some key criterions (for example, livability, rate of pupation and ratio of eclosion, etc. ) is concerned, and was as well as the natural food for the other criterions rest such as pupal period, imago lifespan, fecundity of adult female, egg duration, and hatching rate. However, the larval duration in the third generation fed on the optimized artificial diet was lengthened compared with those on fresh rice stem.

