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Prays oleae Bern, (OM) and Palpita unionalis Hub., (JM) are two of the most important pests in olive groves in Egypt. A 3-year monitoring study using sex pheromone traps in semi-arid and arid olive groves was performed. In the semi-arid grove, flight pattern of the OM was the same as in other Mediterranean countries, but in dates concordating plant phenology. The moth completes three generations annually: the first flight is in March to April, the second is in May to June and the third occurs in August to October. In the arid olive grove, an interesting flight pattern was observed. First flight was always very close or overlapped with the second one with no male catches during August to October. However, eggs were present most of the season, indicating unusually high female presence and oviposition activity of the OM during the absence of males in the traps. Generally, moth densities were significantly lower in low fruiting years than in higher ones and were also lower in the arid olive grove than in the semi-arid one. In contrast, JM males were present all season, exhibiting six to seven and three to four overlapping flight peaks in arid and semi-arid olive groves, respectively. Moth densities were significantly higher in the arid olive grove than those in the semi-arid one. This study shows that trapping location and fruit bearing year are characteristics that strongly affect the grove-specific information needed to estimate correctly adult emergence and thus the timing of control measures.