1. During late spring and most of the summer season the ant,Messor aegyptiacus was active during two foraging periods one in the morning and the second in the evening. During late summer and beginning of the fall it was active only in the morning. 2. The morning foraging activity began before sun-rise about 6.00 a.m. and stopped at about 10.00 a.m. and it was confined to harvesting. The evening activity started at about 6.00 p.m. and came to an end nearly at sun-set. Cleaning the nest of wastes usually occurred in this period. 3. During the morning foraging period there were two peaks of activity one took place in May and the second in August and the level of foraging activity was most high in August. A true evening foraging activity occurred during May and June and there was only one peak of field activity in June. 4. Seeds and fragments of plant leaves and stems formed the main food supply of this ant. 5. The temperature, relative humidity and light intensity showed a remarkable effect on the morning start and evening stop of foraging. Both the wind velocity and cloud cover, within the ranges obtained, did not influence the rate of field activity.