The leafcutting bee, Megachile minutissima Radoszkowski, 1876, is a valuable pollinator of alfalfa grown for seed production in Egypt. In order to control adult emergence of M. minutissima to be synchronized with the expected changes in flowering times of alfalfa crop, breaking the prepupal diapause to initiate the subsequent developmental stages of this insect pollinator is necessary. Laboratory experiments were conducted to estimate the influence of incubation temperature at 30 ± 0.4 °C aft er diff erent intervals of cold storage at 10 ± 0. 4 °C on loose bee cells containing diapaused prepupae, which were obtained during the previous season from the successful nesting straws of the artifi cial nests. Results indicated that the shortest incubation time required for breaking prepupal diapause was about 12 and 19 days to reach the pupal and adult stages, respectively. The percentage of emerged adults was about 60 % at 152 days cold store, and gradually decreased with the increase of cold storage periods in 2009. Meanwhile, the percentage of emerged adults ranged between 40–60 % at all cold storage periods in 2010. Moreover, the results indicated that the optimal period of cold storage at 10 ± 0.4 °C for diapaused prepupae in their loose cells should be between 146 to 153 days, where the maximum rate of adult emergence was occurred. Th e maximum rate of newly emerged males and females of M. minutissima was recorded at 10 % and 26 % in April 26, 2009 and 30 % and 20 % in May 4, 2010, respectively. However, the minimum rate of adult emergence was occurred in August, September and October months.