The age specific life tables for American bollworm Helicoverpa armigera on cotton (var. MCU-5) were constructed. Based on K values, unknown factors which include predation and migration were identified as key mortality factors in the field population of H. armigera, (larval phase-II). The natural biocontrol agents Trichogramma chilonis, Bracon sp, and Nomuraea rileyi contributed some degree of mortality in the pest population. The negative values of trend index (I) in all the generations indicated that mortality factors operating during this period were effective in causing decline in the pest population. none no species