Modulation of sucrose response thresholds in honey bees (Apis mellifera L.): influence of genotype, feeding, and foraging experience

The perception of sugar is important to honey bees for making foraging deci sions. We measured bees' perception by determining what concentration of su crose touched to the antennae elicited the proboscis extension response (re sponse threshold). A low response threshold (extension at low concentration ) suggests a high perceptual value of sucrose, and vice versa. Perception o f sucrose solutions differed between two artificially selected genotypic st rains and was modulated by the bees' recent feeding experiences. Bees offer ed 10%, 30%, or 50% sucrose solutions in small cages overnight, and in larg e flight-cages or free-flying in the field for several days, had subsequent response thresholds positively correlated to the concentration offered. Em pty bees, whether they were nectar., water or pollen foragers, dancers or n on-dancers, had a significantly lower threshold than loaded bees. Crop volu me affected response thresholds directly and independently of sucrose conce ntration. We interpret these findings as multiple mechanisms that operate i n different time scales, modulating perception of sucrose. Changes occurred in the time scale of evolutionary processes as demonstrated by genotypic d ifferences. Changes with foraging experience occur in hours or minutes whil e effects of crop filling are instantaneous.