Title: A Study on Some Biological Aspects of Chilo suppressalis Walker(Lepidoptera: Pyralidae) in Rice Fields of Mazandaran

Some biological aspects of Chilo suppressalis Walker (Lepidoptera: Pyralidae) was studied in paddy fields of Mazandaran during 2007-2008. The studied characteristics were the number of larval instars and developmental time of each stage in two generations. The results indicated that the number of larval instars were different in each generation, including six instars in the first generation and five instars in the second one. Head capsule width of different instars were significantly different and there was not overlap between them in despite of vast range. The mean developmental time of each larval instars were longer in the first generation than the second one. The total mean developmental period in the first generation was determined 1.25 times of the second generation. Therefore the larvae of first generation of C. suppressalis molt once more than the larvae of second generation, and also their developmental time is longer than the second generation larvae.