A series of life tables (22 generations) for the rice yellow stem borer, Scirpophaga incertulas (Walker), a major pest of rice in Bangladesh, was constructed. In a deepwater rice ecosystem, the S. incertulas population dropped to a low level in the second or third generation (May-June), then reached the annual peak level in the fifth generation during September-October. The population dropped again to the lowest level in the sixth generation (November-February) when the larvae remained in diapause for about 3 months. In general, the population suffered very high mortality (99%). The estimated egg mortality was 49%; about 96% of the hatched larvae failed to penetrate into the rice stem; 39% larvae and 27% pupae died inside the stem. The population suffered very high mortality (96 %) at the early larval stage and the resultant survivorship curve was type III. Key factor analysis revealed that the disappearance of newly hatched larvae before penetration into the rice stem was the key mortality factor responsible for population fluctuations between generations. Disappearance of young larvae and egg mortality were density-dependent, but of a weak type.

Time-specific life tables were constructed for the Mexican beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), which is a promising biological control agent of the Neotropical weed, Parthenium hysterophorus L. (Asteraceae) in and around Bangalore, India. Infertility of eggs (46.00–71.10%) was found to be the key mortality factor, followed by death during the pupal stage (15.76–21.38%), as confirmed by key mortality factor analysis and construction of survivorship curves. No parasitoids or predators were recorded on this insect, while some of the dead pupae/pre-pupae (2.27–17.24%) were found to be infected by Metarhizium anisopliae (Metchnikoff) Sorokin. The high generation trend values (305.88–557.14), give an indication of the biotic potential of this insect, which was found to cause rapid defoliation of the weed under field conditions.