Experiments were carried out at the farm of the Agriculture Research Center of the Faculty of Agriculture, Mansoura University during the two successive seasons 2011 and 2012 to investigate some ecological aspects such as seasonal abundance; effect of some weather factors and the annual generation of certain aphid species infesting cowpea plants at Mansoura district. The obtained results recorded three aphid species attacking cowpea plants. These species namely: Aphis cracivora (Koch.), Aphis gossypii (Glov.) and Myzus persicae (Sulz.). The data revealed that, A. craccivora individuals began to appear on the plants on the first week of April and the population fluctuated to reach a maximum on the first week of August in the first season 2011 and in last week of July in the second season 2012.The population density of this insect decreased gradually until the end of October during the two seasons of investigation. The results indicated that, A. gossypii began to appear on cowpea plants in the beginning of April, there after the population fluctuated to reach its maximum in the second week of August during the two seasons of study, then decreased gradually until the end week of October. The obtained results revealed that, M. persicae individuals began to appeared on cowpea plants on the first week of April, there after the population fluctuated to reach its maximum in the third week of July in the first season 2011 and in first week of August in the second season 2012, respectively. Then the population density decreased gradually until the end of October during the two seasons of study. The effect of the temperature and relative humidity on the population density of the three aphid species infesting cowpea plants revealed that the combined effect of these factors exerted positive significant correlation in the two seasons of the study. The results cleared that the temperature and relative humidity effecting greatly on the population density of these aphid species.