Abstract: Through systematical investigation on the population dynamics and analysis of natural population life tables of the cotton bollworm Heliothis arrnigera in both corn and cotton fields in North China, it is concluded that corn fields could serve as themportant habitat of the third generation cotton bollworms and the mortality rate of immature cotton bollworms in corn fields exceeded that in cotton fields. Effect indices of the third generation cotton bollworms in cotton fields were manipulated and analyzed. Among the 7 variables the ratio of corn cultivation area to cotton cultivation area was found to be the active factor and the numbers of eggs laid by the second generation in the cotton fields was ascertained as the key /actor. These conclusions are tested with local data from 1973 to 1991 with satisfactory results.

Key words: Heliothis armigera——population dynamics——life table