A simple regression model for the development of the cotton whitefly population in California cotton was constructed based on the insect's development rate and extensive sampling of adult activity in cotton fields during 1982 and 1983. Distinct peaks and valleys in that adult activity closely follow the generation time of the insect, predicted from developmental data obtained by U. S. Department of Agriculture scientists in Arizona and from prior field observations in the Imperial Valley. In 1984, we attempted to validate the rate of development in the whitefly population which allows us to calculate late summer and fall population levels based on early summer population data. We observed that the actual versus projected whitefly population data followed very closely throughout the season.