author(s)
Supriya GB, Singh TVK, Sunitha V and Vinod SK

abstract
To study the age specific survivorship of S. litura, on Bt cotton hybrids, life tables was constructed in controlled conditions (24±1°C, 70±5% R.H.). During 2012-13. From (December- June). At College of Agriculture, Department of Entomology. Bt-Lab. Professor Jayashankar Telangana State Agriculture University, Rajendranagar, Hyderabad. The age- specific life-table of S. litura on Bt-II hybrids showed maximum survivorship during fourth and fifth instar stages from third instar, mortality was more in the early stages and it gradually declined till culmination of the generation, it has shown type IV survivorship curve. The net reproductive rate (R₀) 101.34 females/ female/day, mean generation time (T_c), 40.93 days, intrinsic rate of increase (r_m) (0.1180), finite rate of increase (λ) (1.12) females/female/day, doubling time (DT) (5.81) days, weekly multiplication rate (WMR) (2.28) times per week, and annual rate of increase (ARI) (5.0929 x 10¹⁸) indicating completion of 18 generations per year, recorded on different Bt-II hybrids revealed less values compared to Bt-I fed larvae. In Bt-II hybrids the life expectancy was less in early days ranged between (20.36-23.51days) and then it increased ranged from (18.19-26.00 days) and decreased gradually with the age. The protein estimation revealed that the amount of Cry 2Ab toxin in Bt-II hybrids was decreased in the leaves (126.20-210.71 ppm) and recorded more in squares (213.24-318.14 ppm) and bolls (343.50-767.08 ppm) during 90-120 DAS. The Bt-II hybrids have shown a profound impact on the growth and development of S. litura during early stages of crop, as the crop matured the Cry toxin content decreased, survival rate recorded was more in 4^th and 5^th instar larvae in later stages of crop.