Tanya Pankiw

The evolution of sociality has configured communication chemicals, called primer pheromones, which play key roles in regulating the organization of social life. Primer pheromones exert relatively slow effects that fundamentally alter developmental, physiological, and neural systems. Here, I demonstrate how substances extracted from the surface of foraging and young pre-foraging worker bees regulated age at onset of foraging, a developmental process. Hexane-extractable compounds washed from foraging workers increased foraging age compared with controls, whereas extracts of young pre-foraging workers decreased foraging age. This represents the first known direct demonstration of primer pheromone activity derived from adult worker bees.

The responsiveness of bees to sucrose is an important indicator of honey bee foraging decisions. Correlated with sucrose responsiveness is forage choice behavior, age of first foraging, and conditioned learning response. Pheromones and hormones are significant components in social insect systems associated with the regulation of colony-level and individual foraging behavior. Bees were treated to different exposure regimes of queen and brood pheromones and their sucrose responsiveness measured. Bees reared with queen or brood pheromone were less responsive than controls. Our results suggest responsiveness to sucrose is a physiologically, neuronally mediated response. Orally administered octopamine significantly reduced sucrose response thresholds. Change in response to octopamine was on a time scale of minutes. The greatest separation between octopamine treated and control bees occurred 30 min after feeding. There was no significant sucrose response difference to doses ranging from 0.2 μg to 20 μg of octopamine. Topically applied methoprene significantly increased sucrose responsiveness. Handling method significantly affected sucrose responsiveness. Bees that were anesthetized by chilling or CO₂ treatment were significantly more responsive than control bees 30 min after handling. Sixty minutes after handling there were no significant treatment differences. We concluded that putative stress effects of handling were blocked by anesthetic.

The perception of sugar is important to honey bees for making foraging decisions. We measured bees' perception by determining what concentration of sucrose touched to the antennae elicited the proboscis extension response (response threshold). A low response threshold (extension at low concentration) suggests a high perceptual value of sucrose, and vice versa. Perception of sucrose solutions differed between two artificially selected genotypic strains and was modulated by the bees' recent feeding experiences. Bees offered 10%, 30%, or 50% sucrose solutions in small cages overnight, and in large flight-cages or free-flying in the field for several days, had subsequent response thresholds positively correlated to the concentration offered. Empty bees, whether they were nectar, water or pollen foragers, dancers or non-dancers, had a significantly lower threshold than loaded bees. Crop volume affected response thresholds directly and independently of sucrose concentration. We interpret these findings as multiple mechanisms that operate in different time scales, modulating perception of sucrose. Changes occurred in the time scale of evolutionary processes as demonstrated by genotypic differences. Changes with foraging experience occur in hours or minutes while effects of crop filling are instantaneous.