Abstract: 【Aim】 To explore the relationship between the testicular volume and mating activity of male moths of the striped rice stem borer, Chilo suppressalis, and to evaluate the effectiveness of sex pheromone trapping in the pest management. 【Methods】 The testicular volume of different day-old male moths of C. suppressalis under different mating statuses and trapped by sex pheromone were measured and compared, and the relationship between the testicular volume and the developmental and mating statuses of male moths was established. 【Results】 The age (day-old) of male moths of C. suppressalis significantly affected their mating activity. The mating rate of the newly emerged (0-day-old) male moths was low, and the mating rate was the highest in the 1-day-old male moth and then decreased gradually as the age (day-old) of male moths increased. There was a significant negative correlation between the testicular volume and the age of male moths of C. suppressalis. The testicular volume of the mated male moths was significantly larger than that of the unmated male moths of the same age. The testicular volume of the male moths caught by pheromone traps was significantly larger than that of the untrapped male moths, but was as large as that of the mated male moths of the same age. The development of the testis in the mated moths was similar to that of the unmated individuals. The testicular volume of male moths caught by sex pheromone traps in the field was smaller than that of the unmated male moths of 0-1-day-old, but larger than that of the unmated male moths of 2-6-day-old. 【Conclusion】 The results indicate a positive correlation between the response of male moths of C. suppressalis to sex pheromone and their testicular volume. Male moths trapped by sex pheromone lures show stronger responding activity to sex pheromone, and most of individuals caught by sex pheromone traps are the unmated ones. Copulation does not affect the testicular volume and the development of the testis of male moths of C. suppressalis. The relationship between the mating ability and testicular volume of male moths of C. suppressalis explains the effectiveness of sex pheromone trapping in pest management, and provides a basis for the mating study of other moths.

Key words: Chilo suppressalis, testis, testicular volume, mating status, sex pheromone, age