Field experiments were carried out at the farm of AgricultureResearchCenter of the Faculty Agriculture, MansouraUniversity during the two successive seasons 2012 and 2013. The obtained results revealed that, six injurious insects were recorded infesting cowpea plants during the two successive seasons, these insect species namely: Aphis gossypii Glover, Aphis craccivora  Koch, Cosmlyce boeticus L., Liriomyza trifolii Burgess, Empoasca lybica Berg, Nezara viridula L. The dominant abundant species was A. craccivora; the lowest abundant species was C .beoticus during the two seasons of study. The data revealed that, A.gossypii had one peak in the first planting date, three peaks in the second planting date and two peaks in the third planting date respectively, during the first season of study. On other hand these insect species had three peaks in the first and the second planting dates, while that was two peaks in the third planting date during the second season of study. Aphis craccivora had one peaks in the first planting date and three peaks in the second and the third planting date during the 2012 season. In the second season of study 2013, this species had three peaks in the first and second plating date and two during twp peaks in the third planting date. Cosmlyce beoticus had two peaks during the first planting date; four peaks recorded in the second planting dates and three peaks in the third date during the two seasons of study. Neara viridula had three peaks occurred in the first date; the second planting date and three peaks in the third date during 2012 and 2013 seasons. The date indicated that E.lybica had two peaks in the first planting date; four peaks during the second planting date and three peaks in the third planting date during the two season of study. The leaf miner L. trifolii recorded three peaks in the first planting date and in the second planting date had two peaks and in the third planting date had four peaks during the first season of study. While in the second season of study, three peaks had occurred in the first planting date and in the second planting date had three peaks and in the third planting date had four peaks.  The effect of the temperature and relative humidity on the population density of the major insect attacking cowpea plants indicated that combined effect of these factors exerted negative or positive significant correlation in the two seasons of study .The results cleared that temperature and relative humidity affected greatly on the population density of the injurious insects