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Task Specialization and Odor Effects on Proboscis Extension Conditioning in Bumblebees (Bombus huntii)

Hannaford, Susannah, Sattler, Amelia, Siegel, Jessica, Foster, Robin L.
Journal of insect behavior 2013 v.26 no.6 pp. 762-779
Bombus, Lavandula, foraging, honey, insect colonies, learning, odors, proboscis, social insects
Workers in a social insect colony have distinct experiences that may affect their performance in a learning task. In this study using free-foraging and flight-cage bumblebee Bombus huntii colonies, the strength of olfactory proboscis extension conditioning (PEC) was affected by a bee’s task specialization as a nurse or forager and the stimulus odor. Nurses (n = 26) learned to respond to the odors 1-hexanol and lavender, but foragers (n = 25) had inhibited conditioning to both odors. More nurses (73 %) than foragers (48 %) had at least one conditioned response (CR), and nurses displayed significantly more CRs than foragers. As expected, a pseudoconditioned control group (n = 9) showed very few CRs. Among bees that were given a second day of trials, nurses—but not foragers—showed modest improvement. Such strong inhibition of PEC has not been described in honeybee or bumblebee foragers. The stimulus odor also affected conditioning strength in nurses. Lavender, a familiar odor, elicited earlier and more CRs than 1-hexanol. We propose that learning floral odors in the context of foraging may inhibit PEC in bumblebee foragers, whereas exposure to odors in the honey stores may prime subsequent learning in nurses.