Tropical stingless bees exhibit pronounced positive phototaxis to the ultraviolet component of sunlight

Abstract

Positive phototaxis, an innate attraction to light, is crucial for bees’ navigation and escape behaviours. With the migration of bee-pollinated crops to greenhouses, alterations in light and temperature within these environments may influence bees’ phototactic responses. We evaluated how the attenuation of UV and green light affected the proportion and latency of the phototactic orientation of stingless bees within a Y-shaped maze, in which sunlight was filtered by different materials at its two edges. We found that three species of stingless bees (Melipona quadrifasciata, Scaptotrigona cf. postica, and Frieseomelitta varia) were more frequently attracted to the edge with a higher incidence of solar UV light and exhibited shorter orientation latencies than to the opposite edge, which had virtually no UV transmittance and lower green light transmittance. Under conditions of low UV light at both ends of the maze, neither a higher proportion of green light nor greater total light intensity influenced the phototactic orientation of the three species towards a particular maze arm. These findings indicate that UV light is a key component of the phototactic response in the tropical bee species studied and should be considered when employing these species for pollination services in protected environments with low UV incidence.