The influence of constant temperatures (20, 25, 30 and 35 °C) as accumulated heat units (day degrees) on the emergence and stages of development of the pink bollworm (PBW) (Pectinophora gossypiella).has been studied under laboratory conditions of the constant temperatures of 20, 25, 30 and 35°C The observed incubation periods, rate of development, the theoretical lower threshold of development (t₀) and the degree days (DD_S) of each stage were estimated. Generally, the obtained results showed a negative relationship between incubation temperatures (°C) and lengths of incubation periods for all PBW stages. Referring to the constant temperatures, the PBW stage periods were varied between 20°C and 35°C, hence, They ranged from 7.2 to 2.87, 30.89 to 7.76, 24.4 to 9.83, 4.28 to 1.26, 6.3 to 2.8 and from 6.1 to 2.6 days for eggs, larvae, pupae, pre-oviposition period, oviposition period, post-oviposition period , consequently. The estimated lower threshold temperature (t₀) has been differed according to the developmental stage. The (t₀) values were 10.63, 14.82, 9.28, 12.19, 8.44 and 7.53 °C for eggs, larvae, pupae, pre-oviposition, oviposition, post-oviposition periods, respectively. The thermal units as degree days (DD's) were also calculated for each immature and mature stages. The heat unit's accumulations as a part of IPM could be of  benefit for forecasting population  of  the different  PBW stages, which were highly important for the predicting  pest population and  applying  insecticides at the optimum time to obtain timely insect control.