We studied associative visual learning in harnessed honeybees trained with monochromatic lights associated with a reward of sucrose solution delivered to the antennae and proboscis, to elicit the proboscis extension reflex (PER). We demonstrated five properties of visual learning under these conditions. First, antennae deprivation significantly increased visual acquisition, suggesting that sensory input from the antennae interferes with visual learning. Second, covering the compound eyes with silver paste significantly decreased visual acquisition, while covering the ocelli did not. Third, there was no significant difference in the visual acquisition between nurse bees, guard bees, and foragers. Fourth, bees conditioned with a 540-nm light stimulus exhibited light-induced PER with a 618-nm, but not with a 439-nm light stimulus. Finally, bees conditioned with a 540-nm light stimulus exhibited PER immediately after the 439-nm light was turned off, suggesting that the bees reacted to an afterimage induced by prior adaptation to the 439-nm light that might be similar to the 540-nm light.

The learning ability of the European honeybee, Apis mellifera, is well known. However, in a proboscis-extension reflex (PER) assay, newly emerged and very young worker bees could not associate a given odor (conditioned stimulus, CS) with a sucrose reward (unconditioned stimulus, US): This ability was acquired 5 to 9 days after emergence in workers, while it was accomplished 2 to 5 days after emergence in drones, probably reflecting the earlier onset of flight in drones. When workers are reared individually in a confined condition deprived of colony odor and other social stimuli, they do not develop the ability even after 9 days after emergence. In a series of experiments subjecting the bees to the confined condition for various lengths and timings, the important period for acquiring the learning ability was from day 2 to 6 after emergence. However, even bees that acquired the ability lost it when exposed to the confined (stimuli-deprived) condition for the next 15 days, meaning that the continuous input of appropriate sensory stimuli is essential for both acquiring and maintaining the learning capability.