No abstract

During foraging, worker bumblebees are challenged by simple to complex tasks. Our goal was to determine whether bumblebees could successfully accomplish tasks that are more complex than those they would naturally encounter. Once the initial training to successfully manipulate a simple, artificial flower was completed, the bees were either challenged with a series of increasingly difficult tasks or with the most difficult task without the opportunity for prior learning. The first experiment demonstrated that the bees learned to slide or lift caps that prevented their access to the reinforcer sugar solution through a series of tasks with increasing complexity: moving one cap either to the right or to the left, or lifting it up. The second experiment demonstrated that the bees learned to push balls of escalating masses (diameters 1 and 1.27 cm) from the access to the hidden rewarding (sugar syrup) reservoir of artificial flowers. In both experiments, when bees with experience with only the simplest task (i.e. an artificial flower without a barrier to the reinforcer) were presented next with the most complex or difficult task, they failed. Only by proceeding through the series of increasingly difficult tasks were they able to succeed at the most difficult. We also noted idiosyncratic behaviours by individual bees in learning to succeed. Our results can be interpreted within the context of Skinnerian shaping and possibly scaffold learning.

Bumblebees move about their environments by flying and by walking. Most experimental studies have addressed navigation during foraging flights, but we presented our experimental bees with the challenge of learning to navigate while walking as they must do in nature within topographically complex spaces containing their nests. We trained bumblebee workers to navigate complex, nine-channel, mazes in the absence of specific visual, chemical or textural cues. They successfully navigated through complex multi-turn mazes (stereotypical "rat mazes") with several dead-ends by memorizing the entire sequence of appropriate turns, and their choice of correct first turn on entering the maze. Thus, their observed proficiencies indicated that the individual bumblebees had each memorized the maze by learning motor sequences which were not linked to visual, chemical or textural stimuli, and that their memories were triggered by contextual cues associated with the bees' positions in a sequence. Our findings have implications on natural ambulatory activities inside and outside the colony, and even in practical use as vectors of biological control agents.

Social learning occurs when one individual learns from another, mainly conspecific, often by observation, imitation, or communication. Using artificial flowers, we studied social learning by allowing test bumblebees to (a) see dead bumblebees arranged in foraging positions or (b) watch live bumblebees actually foraging or (c) communicate with nestmates within their colony without having seen foraging. Artificial flowers made from 1.5 mL microcentrifuge tubes with closed caps were inserted through the centres of blue 7 cm plastic discs as optical signals through which the bees could not forage. The reinforcer reward syrup was accessible only through holes in the sides of the tubes beneath the blue discs. Two colonies (A and B) were used in tandem along with control (C and D) colonies. No bee that was not exposed (i.e., from the control colonies (C and D)) to social learning discovered the access holes. Inside colony B, we imprisoned a group of bees that were prevented from seeing or watching. Bees that saw dead bumblebees in foraging positions, those that watched nest-mates foraging, and those that had only in-hive communication with successful foragers all foraged successfully. The means of in-hive communication are not understood and warrant intense investigation.

Mobility of flowers in the wind has been proposed to affect the performances of pollinators in landing on flowers, nectar extraction, and pollen dispersal. Our study examined the preferences of worker Bombus impatiens Cresson (Hymenoptera: Apidae) for landing on and feeding from immobile or mobile artificial flower. Mobile flowers moved at varied frequencies (0.1–3.0 Hz) and in different directions, horizontal H (left to right wave) and vertical V (from en-face presentation at the lowest point to horizontal presentation at the zenith). We found that the bees showed no preference for mobile or immobile flowers. In general, we found that landing ability (time spent from the bees entering the testing arena to landing and starting to feed on the artificial flower) decreased as frequency (Hz) or speed of motion (cm/second) increased. Directionality of waving affected performance with the bees being able to forage from horizontally moving flowers better than from vertically moving flowers. Experience played a major role in improving individual performances. We also found that the bees could differentiate between horizontally and vertically waving flowers as well as between frequencies or speeds of motion.