The changes in the population density of sugarcane internode borer,Chilo sacchariphagus indicus(Kapur), and their causes were quantified on susceptible sugarcane variety Co.6304 planted during early and late main season in 1979 and on susceptible Co.6304 and resistant CoJ.64 during 1980 under artificial infestation conditions. The 1979 life tables showed an increasing trend index of 1.24 and 1.16 of cohort population in early and late main season planted crops respectively. The 1980 life tables showed an increasing trend by 2.42 times on Co.6304 while the cohort showed a trend index of 0.57 on CoJ.64 indicating the decline in population density. The survivorship curves fitted to type IV of Slobodkin indicating that high mortality occurred in the early stages of the Insect life cycle. The mortality factors included parasitization by hymenopterous parasites, arthropod predation, desiccation, infertility and wind in egg stage, suspected arthropod predation and dispersal loss in the first instar and migration and unknown losses, parasitization and granulosis virus infection during the other larval instars. Pupal mortality was caused by the failure to emerge due to unknown reasons, parasitization and virus infection. TheK‐factor analysis showed suspected arthropod predation and dispersal loss during the first instar and loss due to migration and unknown causes in other larval instars were the key mortality factors. The list of hymenopterous parasites, suspected arthropod predators and pathogens was also given and their role was discussed.