Seasonal Rates of Increase for a Population of the Boll Weevil, Anthonomus grandis, in the High and Rolling Plains of Texas1

Life, fertility, and life-expectancy tables, were computed for 13 boll weevil cohorts reared in field cages and in an insectary. The increase in female offspring per female per week ranged from 1.56 for adults produced from eggs deposited Aug. 16, 1966, to 0.63 for eggs deposited Sept. 26, 1966. However, the number of female offspring produced per female per generation ranged from 20.6 for adults emerging from eggs deposited Aug. 30, 1966, to 0.02 for eggs deposited Oct. 3, 1966. Seasonal life expectancy for eggs during 1966 ranged from about 1 to 7 weeks for eggs deposited Aug. 2 and Sept. 29, respectively. However, the life expectancy of teneral adults ranged from almost 3 to 10 weeks during this same period. Thus, adults had a greater life expectancy than eggs. Adults emerging from cohorts started after mid-August had lower mortality rates than cohorts started during July to mid-August. This fact indicates that adult numbers should tend to accumulate in cotton fields after mid-August.