A new study published in the Proceedings of the National Academy of Sciences reveals that bumblebees exhibit distinct facial expressions resembling 'liking' and 'disliking' responses, providing further evidence for insect sentience. When presented with a sweet solution, bees extend their glossa (insect tongue) after drinking, akin to licking their lips. In contrast, they respond to unpleasant tastes like salt or quinine by shaking their heads and wiping their mouths.
Study Methodology and Findings
Conducted by researchers from Macquarie University and Southern Medical University in China, the study presented bumblebees with droplets of various solutions: 60% sugar, 20% sugar, plain water, 5% salt, or 1 millimolar quinine. Their reactions were recorded on slow-motion video. Under normal conditions, bees displayed 'post-consumption glossa' after tasting sweet solutions, continuing to lick even after finishing the drink. For salt or quinine, they showed clear distaste.
Prof Andrew Barron, an insect behavior researcher at Macquarie University and co-author, stated: 'Facial expressions are an important window into the internal states of animals. What we found is that bees show responses with their mouthparts to solutions that indicate their subjective like or dislike of those solutions. It tells us there is an inner life to the insect.'
Context-Dependent Responses
To ensure the reactions were not mere chemical reflexes, the team tested 18 colonies under varying conditions, including heat stress, satiation, and drug administration. The bees' responses changed with context. For example, heat exposure altered their reaction to water or salty solutions from neutral or averse to positive. Barron likened this to humans craving an electrolyte drink after intense exercise.
Associate Prof Thomas White, an entomologist from the University of Sydney not involved in the study, noted that research into insect behavior and sentience is 'a fast moving field.' He highlighted that this study focuses on the 'positive side of life,' as most research investigates negative feelings like pain or fear.
Implications for Insect Sentience
The findings challenge traditional views of insects as mere 'mini robots.' White commented: 'The picture is increasingly pushing towards a view that insects, or many insects, have some simple capacity to feel the world, not just to assess it and detect it and process information but to actually have a point of view.' He acknowledged that this concept is challenging for some, as it raises ethical questions about our responsibilities toward insects.
Barron added: '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.'
