High-resolution video has revealed that bumblebees react to tastes with specific mouth and head movements, responses that change according to what they have just consumed and how their bodies stand at that moment. The work, published this month in the Proceedings of the National Academy of Sciences, examined Bombus terrestris and documented behaviours that echo patterns seen in other animals yet arise from an invertebrate nervous system.
Bees given sweet solutions extended their glossa, the tubular tongue-like structure, after feeding. In contrast, those offered bitter or salty droplets shook their heads or wiped their mouths. These postconsumption actions varied with concentration. A 60 percent sugar mix produced strong glossa protrusions. Plain water and weaker 20 percent sugar elicited milder responses. Salt at 5 percent and quinine at one millimolar triggered the aversive head-shakes and mouth-wipes.
The reactions were not fixed reflexes. Internal physiological states altered them. Dehydrated bees held at 40 degrees Celsius showed increased glossa protrusions even to salty droplets, according to New Scientist. The finding suggests the taste evaluation itself shifts with the animal's condition.
Treatment with endocannabinoids boosted the enjoyment-linked glossa extension, while dopamine influenced desire but left the enjoyment marker unchanged, New Scientist reported. Such pharmacological probes add weight to the idea that these movements track something beyond simple attraction or avoidance.
Researchers from Macquarie University in Australia and Southern Medical University in China collaborated on the project. Lead authors Yonghe Zhou, Andrew Barron and Fei Peng designed experiments that presented taste droplets directly to bees from 18 colonies. Slow-motion and high-frame-rate footage allowed them to dissect movements too rapid for ordinary observation.
The paper, titled Bumblebees’ orofacial reactions to tastes provide evidence for affective evaluation, stops short of claiming insects feel emotions in the human sense. Instead it offers observable markers that vary with internal state, much as facial expressions in mammals have long been studied. This measured approach respects the limits of what behaviour alone can reveal while exposing previously hidden order in insect biology.
