A new study reveals that bumblebees display distinct facial expressions when tasting different solutions, indicating they may have an inner life. When bees taste something sweet, they extend their glossa (tongue) repeatedly, akin to licking their lips. In contrast, they shake their heads and wipe their mouths after tasting bitter or salty substances. These behaviours, captured on slow-motion video, are consistent with 'liking' and 'disliking' responses observed in mammals.
Study Methodology and Findings
Published in the journal Proceedings of the National Academy of Sciences, the study was a collaboration between Macquarie University and Southern Medical University in China. Researchers presented bumblebees with droplets of 60% sugar, 20% sugar, plain water, 5% salt, or quinine (1 millimolar concentration) and recorded their reactions. Under normal conditions, bees displayed 'post-consumption glossa' after sweet solutions—they kept licking even after finishing drinking. For salt or quinine, they showed clear distaste.
Professor Andrew Barron, an insect behaviour 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, scientists tested 18 colonies under various conditions, including heat stress, satiation, and drug administration. The bees' responses depended on context. For example, heat exposure changed their reaction to water or salty solutions from neutral or averse to positive. Barron likened this to a person who would normally dislike an electrolyte drink but finds it appealing after a long, hot run.
'If a rat gets a salty taste it doesn’t like, it wipes its mouth parts, wipes its whiskers, wipes its tongue,' Barron said. 'And we see something similar in a bee.'
Implications for Insect Sentience
While similar findings in mammals are readily accepted, the concept of an inner life in insects remains 'highly controversial,' Barron noted. Associate Professor Thomas White, an entomologist from the University of Sydney not involved in the study, described insect sentience research as '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.
'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,' White said. He added that this challenges people's intuitions about where to draw the line in the animal kingdom regarding ethical responsibilities.
'There’s always been a tension between thinking of insects as animals, or some sort of mini robots,' Barron said. 'This is another step towards showing there’s an inner life to being a bee.'
