A preliminary research on protandry in rice striped stem borer

Key Words： Chilo suppressalis, immature period, protandry, emergence, sex pheronmone trap

Abstract：Protandry is defined as males emerging before females and is a common phenomenon among Lepidoptera. Protandry has been considered a strategy to promote reproductive success and may prevent inbreeding depression; generally a heavy cost for many Lepidoptera. The rice striped stem borer, Chilo suppressalis Walker (Lepidoptera:Pyralidae), is an important pest of rice in China. We noticed that males of this species emerged earlier than females. We collected empirical data to determine the period from hatching to adult emergence, also called the immature period. The results show that the immature period of males was 38.8 d but that of females was 40.6 d. Therefore, on average, males emerged 1.8 d earlier than females. In other words, the protandrous period in C. suppressalis is 1.8 d. The biological significance of protandry, and the use of sex pheromone traps to detect the occurrence of striped stem borer in field conditions, is discussed.