Swimming scototaxis varies among honey bee species

Honey bees can swim on the water surface toward a dark region, a behavior known as scototaxis that facilitates escape from water. Although scototaxis has been documented in honey bees and solitary bees, little is known about how its strength varies among honey bee species. We compared swimming scototaxis in four honey bee species representing two nesting types: open-nesting (Apis florea and A. dorsata) and cavity-nesting (A. cerana and A. mellifera) honey bees. All four species exhibited significant directional swimming toward a dark sector. However, open-nesting species showed significantly stronger scototaxis than cavity-nesting species. No differences were detected between replicate colonies or between species within the same nesting type, whereas a highly significant difference was observed between nesting types. In contrast, swimming distance, duration and velocity did not differ consistently between nesting types. These results demonstrate substantial variation in swimming scototaxis among honey bee species while showing that orientation behavior is dissociated from locomotor performance. Because nesting ecology and phylogenetic position are closely aligned within Apis, the present study cannot distinguish between ecological and evolutionary explanations for the observed pattern.