The present study focused on determining: the developmental rate of the fall armyworm Spodoptera frugiperda at four constant temperatures, (21±1, 24±1, 29±1 and 34±1°C), the number of degree-days (DD's) needed for each stage to finish development, and overall egg-to-adult development, to compute certain biological parameters used in pest prediction. According to the study the development of one generation required around 21, 26. 44 and 47 days at 21, 24, 29 and 34°C. the mean incubation periods were determined to be 4.4, 3.7, 2.1 and 1.3 days at 21, 24, 29 and 34°C, respectively. As the temperature rose, the mean amount of time needed for the adult stage to mature the ovaries and begin laying eggs dropped (from 6.1 days at 21°C to 3.1 days at 34°C). Recorded were generation time, (r_m) and (λ), threshold of development (t₀), and the average thermal units in degree-days (DD's). The research of heat requirements of the pest is very important to calculate the thermal heat units that is necessary for this invasive pest's growth and development, hence the annual field generations can be predicted in addition to draw up a planning IPM strategy for this harmful pest.