Abstract: Diapause of prepupae of the alfalfa leafcutter bee, Megachile rotundata (F.) is mainly controlled by both photoperiod and temperature. A main factor for female is the photoperiodical vari-ation that decides whether progeny prepupae will enter diapause or not. For immature stages, especially from late instar (about third instar) to prepupae, temperature variation has a greater effect onprepupa diapause. During this stage, if the temperature is below (21.09±1.03)12, more than 50 percent prepupae will enter diapause. In addition, the latitude of the area bees being released in and the generation of the bee also have an important influence on prepupae's diapause.

Key words: Megachile rotundata (F.), diapause, inducing factors