The alfalfa leafcutting bee, a solitary pollinator for alfalfa seed production, undergoes facultative diapause in the prepupal stage. Most early season progeny complete development to produce a second generation whereas most late season progeny diapause as prepupae. The cues regulating diapause incidence are not completely understood. To determine the effects of temperature, photoperiod, and population density on diapause incidence, we designed and installed six replicate nest boxes in alfalfa fields near Fargo, ND. We expected that there would be a temperature dependent response of diapause incidence in which larvae experiencing temperature units above a threshold will diapause and the flip in the diapause incidence would occur in response to a decreasing rate of daylength. Similar to our previous results, diapause incidence within a nested cohort was strongly influenced by the conditions experienced by the mother bee, we expected that increased population density would increase diapause incidence. Understanding the cues regulating the diapause incidence will help in sustainable bee management.