Twelve-week diapause optimizes colony production in commercial rearing of <i>Bombus terrestris</i> (Hymenoptera: Apidae)

Bombus terrestris (Linnaeus, 1758) is a crucial pollinator for global greenhouse cultivation and is mass-reared for commercial pollination services in China. Diapause is an indispensable phase in the commercial production of B. terrestris, yet the optimal duration for maximizing colony output remains undefined. We conducted a large-scale study within a Chinese industrial rearing pipeline, assigning 2,455 B. terrestris queens to one of eight diapause durations (0, 4, 8, 12, 16, 20, 24, and 28 wk). Compared to non-diapause controls, diapause significantly improved reproductive performance and shortened colony development cycles. Reproductive success peaked at 12 wk, with 98% egg-laying success, 80% colony foundation success (ie colonies reaching ∼10 workers), and 64% medium colony success (ie colonies reaching ∼60 workers). Queen survival decreased significantly after 16 wk of diapause. Using orthogonal partial least-squares discriminant analysis, we identified seven reproductive performance indicators that contributed most to discriminating among diapause durations (eg time to first male emergence, colony foundation success). Post-diapause physiological status correlated with subsequent colony performance; in this dataset, queens with higher reproductive success tended to exhibit free water content around 55%, glycogen levels between 24 to 37 mg/g, and protein levels between 113 and 134 mg/g at diapause termination. Our findings identify a 12-wk diapause as associated with the highest reproductive performance in this commercial B. terrestris rearing system, offering a practical reference for similar operations.