Biological studies were carried out in the laboratory of Scale Insects and Mealybugs Department, Plant Protection Research Institute, Sharkia Branch, Egypt during the period extended from 2010–2016 years on the citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae) to study the effects of different host plants and temperatures on some biological aspects of the pest to use these useful information for  mass rearing and designing a comprehensive pest management program and prediction models for the citrus mealybug. The accumulated degrees days (ADD) for male and female stages were also calculated. The obtained results obviously showed that there were significant effects on developmental periods, adult longevity, life cycle and generation period of P. citri when reared on pumpkin fruits compared with those reared on potato sprouts. The periods of citrus mealybug stages were significantly reduced gradually by increasing of rearing degree of the tested temperatures i.e. 20, 25 and 30˚C. The mathematical method showed that the accumulated degree days which required for completing one generation for females was 418.11 ADD unit.