The biology and fluctuation of Anticarsia gemmatalis was studied in soybean fields to determine the key stage and factor. Experiments were conducted from 1992 through 1997. Two biological studies were performed each year. In each season, the natural occurrence of eggs and larvae were determined, which allowed the construction of ecological life tables. The net reproduction rate of the species was observed to increase 2.9-to 7.5-fold in relation to the initial population, but the increse was estimated as 15.5-fold for the life table constructed from the averages of annual values. Mean duration time for progenies varied from 33.5 to 40.2 days (mean of 37.9), leading to an average survival per generation between 1.2 and 3.2% (mean of 6.6). The key stage of the population was not determined due the observed low R2. The key factor accounting for population mortality was the fertility of females.
bioecology; velvetbean caterpillar; soybean