Nutritional value and taste play different roles in learning and memory in the honey bee (Apis mellifera)

Honey bees will learn to respond to an odor when their antennae are stimulated with sucrose, even if they are not fed during the conditioning phase. However, if they are not fed, the memory of this association is significantly reduced 24 h after conditioning. These results suggest that stimulation of proboscis with sucrose and/or the nutritional quality of the reward plays an important role in establishing a long lasting memory. Three sugars, xylose, sorbitol and mannitol, are used to investigate the relationship among learning, sensory perception and nutritional value. The proboscis extension reflex is used to show that honey bees cannot taste these sugars, whereas mortality data suggest that bees can metabolize all three sugars. Feeding with sorbitol or xylose during olfactory associative conditioning restores robust 24 h memories. However, when given a free choice between consuming sucrose alone or sucrose supplemented with these nutritional sugars, bees did not show a preference for food containing the higher nutritional content. Furthermore, bees did not ingest solutions containing only the tasteless sugar even when it was the only food source. Together, these results suggest that nutritional content and not just sensory information is important for establishing long term memories, but that bees may not be able to assess nutritional content when it is disassociated from taste.