Slow-motion video reveals that buff-tailed bumblebees (Bombus terrestris) respond to sweet and bitter tastes with distinct, context-dependent behaviors resembling mammalian expressions of pleasure and disgust, adding fresh evidence to the debate over insect consciousness.
Zhou et al. show that buff-tailed bumblebees (Bombus terrestris) display analogous orofacial reactions to tastes that reflect affective evaluation, rather than simple feeding reflexes or motivation. Image credit: Ralphs Fotos.
“This revelation changes our scientific understanding of the inner life of insects,” said Macquarie University’s Professor Andrew Barron.
“Facial expressions are an important window into the internal states of animals.”
“There’s always been a tension between thinking of insects as animals or some sort of mini robots.”
“This is another step towards showing there’s an inner life to being a bee.”
For their study, Professor Barron and his colleagues used a total of 18 colonies of buff-tailed bumblebees.
They isolated individual insects in observation tubes and trained them to locate and consume tiny droplets of 20% sugar water presented just beyond the reach of their antennae.
The bees quickly learned to extend their mouthparts (proboscis) and consume each presented droplet.
The researchers then recorded the insects’ facial and mouthpart movements after they consumed test droplets containing either concentrated or diluted sugar water, plain water, salt water or quinine, a bitter compound.
The insects displayed distinctly different orofacial behaviors after consuming sweet liquids versus bitter and salty liquids.
Post-consumption glossa (tongue) protrusions — akin to ‘licking their lips’ — occurred after eating sugar solutions.
Aversive head shaking and mouth wiping occurred after tasting salty and bitter liquids.
“Many people are comfortable saying that insects can sense, learn, and make decisions, but much less comfortable saying that they may evaluate things as pleasant or unpleasant,” said Professor Fei Peng, a researcher at Southern Medical University.
“Our findings push on that intuition.”
“We don’t yet understand what the bees truly experience, but we can observe emotion-like behaviors,” Professor Barron said.
“What’s important is we’ve now got a practical read on their inner life that we can work with experimentally.”
“The implications extend beyond bees to all insects,” he added.
“In terms of how the brain is organized, there’s no major difference between a bee and a fly — this means there’s more to consider in terms of how we might treat or react to insects.”
“By human standards, the bee brain is tiny — weighing less than a milligram — and yet our evidence suggests the remarkable bee brain can support a form of bee inner life.”
“The work is an important step toward understanding how brain activity relates to subjective experience.”
“We hope further studies will show how the bee’s mental life arises from mechanisms in the brain so we can close the gap between the mental and the physical.”
The study was published July 6 in the Proceedings of the National Academy of Sciences.
_____
Yonghe Zhou et al. 2026. Bumblebees’ orofacial reactions to tastes provide evidence for affective evaluation. PNAS 123 (28): e2529114123; doi: 10.1073/pnas.2529114123
