Many invasive insect pests show phenotypic variation between local populations across their geographical range. Understanding and integrating such differences will help to improve pest management. Population differences are the result of local adaptation to environmental conditions and may be detected using ecological analyses. Immature stages may represent especially interesting study objects as they represent important stages in the life cycle of insects and in many cases may be the most destructive stage. The alfalfa weevil, Hypera postica (Gyllenhal, 1813), is a variable worldwide pest that heavily damages alfalfa fields and is widely distributed in Iran. The lack of information about Iranian populations of H. postica has motivated us to examine immature life stages of three western populations (Karaj, Hamedan, Tuyserkan) and one eastern population (Jovein) under laboratory conditions. We measured the percentage of survival and the developmental times of each immature stage. The results suggested that the mean duration of the pupa stage significantly differs among the eastern population and all western populations (P < 0.005). Egg survivorship was lower in the eastern population (72.5%). The importance of differences in development times between populations is discussed in regards of pest management strategies.