Mean developmental rate of immature cotton leafworm stages and generation at 4 constant temperature regimes over the range of 17.5 to 32.5 c with increments of 5.0 c is fit with a thermal summation (linear regression) and logistic curve. Egg didn't hatch at 10 c and 37.5 c, larvae and pupae also exhibited high mortality at 37.5 c. The developmental rate of all cotton leaf worm stages increased with rise of temperature over range of 17.5 c to 32.5 c. Embryonic, larval, pupal, maturation (pre ovi position period), ovi position and generation threshold temperatures were estimated at: 11.81, 12.5, 11.33, 10.66, 10.8 and 12.6.

Thermal summation, linear and logistic models were chosen to express the relationship between temperature and developmental rates. However, the logistic showed the highest accurate simulation for this relationship.

Upper thermal thresholds as well as other biological constants such as thermolability. Coefficients and thermal units were also estimated.