Photoperiod during nest construction influences diapause status in the alfalfa leafcutting bee (Hymenoptera: Megachilidae)

Authors: RINEHART, JOSHUA - North Dakota State University; NASH, SARA - University Of Arizona; FOSTER, KEEGAN - University Of Rhode Island; Rinehart, Joseph; BOWSHER, JULIA - North Dakota State University

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2025
Publication Date: 7/23/2025
Citation: Rinehart, J., Nash, S.E., Foster, K.J., Rinehart, J.P., Bowsher, J.H. 2025. Photoperiod during nest construction influences diapause status in the alfalfa leafcutting bee (Hymenoptera: Megachilidae). Annals of the Entomological Society of America. https://doi.org/10.1093/aesa/saaf029.
DOI: https://doi.org/10.1093/aesa/saaf029

Interpretive Summary: Photoperiod is the primary environmental factor that many insects use to determine diapause status. In the Alfalfa Leafcutting Bee, Megachile rotundata, long photoperiods lead to a nondiapause response whereas short photoperiods lead to a diapause response. However, it is unknown at what point in the life cycle this species interprets photoperiod to determine diapause and whether this decision is made by the mother or offspring. This study aims to answer these questions by subjecting mothers to three different photoperiods while developing in an incubator and three different photoperiods while nesting in the field during different times of the year. Once nesting was completed the offspring were subjected to the same photoperiods as the mothers in an incubator during offspring development.

Technical Abstract: Diapause initiation is determined by photoperiod and temperature in many insect species. In the solitary cavity-nesting bee Megachile rotundata, which diapauses as a prepupa, photoperiod is an important cue for diapause induction. However, it’s unknown if the mother or offspring make the decision to induce diapause or when this decision is made. Our goal was to answer these questions by manipulating photoperiod during different stages of development in M. rotundata. We subjected mothers to three different photoperiods while they were developing in an incubator and released them into the field to make offspring when those same photoperiods could be observed naturally. Offspring were collected and subjected to the same artificial photoperiods as the mothers. We examined the effects of each photoperiod on offspring diapause as well as reproductive output by measuring the number of nests and brood cells created in each photoperiod. Our findings determined that the photosensitive period occurs in the field, suggesting that the mother determines diapause during nest construction. We also found that reproductive output is the highest during the shortening photoperiods associated with midsummer. This study furthers our understanding of how diapause functions in Megachile rotundata and could be used to advance commercial management practices.