Nectar on tap: Fermentation time and bumble bee preference

Yeasts are common floral inhabitants that produce volatile compounds capable of attracting insect visitors, including bumble bees. The floral specialist yeast, Metschnikowia reukaufii, has been shown to have effects on bumble bee visitation to flowers ranging from neutral to positive, yet key questions remain about how this interaction unfolds over time and in ecologically realistic conditions. In particular, it is unclear how the duration of nectar fermentation influences bee attraction and whether microbial metabolites persist or accumulate within the nest environment.

To address these questions, we conducted behavioral assays using Bombus impatiens workers from eight laboratory-reared colonies in spring 2025. Our study had two primary aims: (1) to quantify yeast abundance, ethanol content, and sugar concentration in bumble bee honey over colony development; and (2) to determine whether B. impatiens workers preferred consuming nectar fermented by M. reukaufii for different durations (2-10 days), and whether ethanol concentrations (0.5–2% ABV) modulated this response. By combining microbial, chemical, and behavioral data, this work advances understanding of the presence of yeasts and fermentation metabolites in stored nectar in bumble bee nests and their role in shaping foraging behavior at the colony level.