Dim-light colour vision in the facultatively nocturnal Asian giant honeybee, .

We discovered nocturnal colour vision in the Asian giant honeybee a facultatively nocturnal speciesat mesopic light intensities, down to half-moon light levels (approx. 10 cd m). The visual threshold of nocturnality aligns with their reported nocturnal activity down to the same light levels. Nocturnal colour vision in is interesting because, despite being primarily diurnal, its colour vision capabilities extend into dim light, while the 'model' European honeybee is reported to be colour-blind at twilight. By employing behavioural experiments with naturally nesting colonies, we show discrimination of the trained colour from other stimuli during the day, and significantly, even at night. Nocturnal colour vision in bees has so far only been reported in the obligately nocturnal carpenter bee The discovery of colour vision in these two bee species, despite differences in the extent of their nocturnality and the limitations of their apposition compound eye optics, opens avenues for future studies on visual adaptations for dim-light colour vision, their role in pollination of flowers at night, and the effect of light pollution on nocturnal activity in a ubiquitous pollinator in natural, agricultural and urban habitats in the Asian tropics and sub-tropics.