The temperature-dependent development of red and green morphs of the green peach aphid, Myzus persicae (Sulzer), was compared on flue-cured tobacco, Nicotiana tabacum (L.), at moderate to high constant temperatures in the laboratory. The red morph was found to develop faster and reproduce more than the green morph at temperatures that promoted the most rapid population growth of either morph. In addition, mean longevity of the green morph was increasingly and significantly shorter than the red morph as temperature increased above the mutual optimum temperature (25 °C) for population increase. Study of the growth of GPA populations on commercial flue-cured tobacco farms in Virginia indicated the initial GPA population is highly aggregated. As the population increases, it becomes increasingly more randomly dispersed within the field. The typical pattern of temporal development of GPA was a bimodal distribution with the greater proportion of individuals occurring after topping of the crop. Cumulative proportional population growth models using degree-days were able to adequately describe growth of populations only on individual farms. Study of the within-plant distribution of GPA found that populations developed colonies of greatest intensity on the youngest leaves. The proportion of the total GPA population found on each leaf occurring on the lower leaf surface decreased with ascending leaf position. In addition, the proportion of the total plant population found on the lower leaves was highest as the crop approached the topping stage. / M.S.