Peach fruit fly (PFF), Bactrocera zonata (Saunders) and Mediterranean fruit fly (MFF) are the most destructive insect pests of fruit and vegetables in Egypt. The current study was carried out over two successive years; 2012 and 2013 in thirteen districts of El-Beheira governorate and aimed to conduct a delimit survey and monitor the seasonal activity of PFF and MFF populations. The results showed that the PFF was recorded in almost all of the examined districts except for Edko district. Moreover, the PFF was not found in El-Mahmodiya district throughout the second study period, while the MFF was spread throughout all tested districts at both years. Inter–site comparison revealed significant differences in the abundance of PFF and MFF across the tested districts during 2012 and 2013 seasons. A significant positive correlation was reported between the population activity of PFF and MFF through 2012 (r=0.34), while a non-significant positive correlation (r=0.24) was obtained in 2013. Population growth rate (r₀) of PFF was higher than that of the MFF through the first interval of population increase through both 2012 and 2013 seasons; 1.02 and 0.17 for PFF, and 0.83 and 0.13 for MFF, respectively. The r₀ values of the MFF was higher than the PFF through the second interval of increase through both tested seasons; 1.04 and 1.10 for MFF, and 0.16 and 0.21 for PFF. It could be concluded that these two insects exchange their role as a key-pest of fruit hosts along the tested seasons.