There is a saying, "If it's sweet, swallow it; if it's bitter, spit it out." It refers to behavior that seeks only one's own interest. For honeybees, it should be, "If it's sweet, stick out the tongue; if it's bitter, wipe the mouth." It turns out honeybees also show emotions on their faces.
Researchers at Southern Medical University in China said on the 6th (local time) that they captured bumblebees (scientific name Bombus terrestris) shaking their heads and wiping their mouths when they dislike food, and licking their lips when they like it, in a paper published in the Proceedings of the National Academy of Sciences (PNAS).
The bumblebee is an insect in the family Apidae and the genus Bombus, and is a pollinator widely used for crop pollination. It has a black, plump body with orange or yellow bands. In English, it is called the bumblebee.
Andrew Barron, a co-author of the paper and a professor at Macquarie University in Australia, said, "Bumblebees don't just need something; they seem to reveal their feelings when they are pleased or when they like something," adding, "This discovery will change the scientific understanding of the inner world of insects."
◇ Faces showing like or dislike by taste
It has been successively revealed that honeybees use tools, recognize human faces, can count up to four, and even possess the concept of "0." But it has been difficult to determine whether honeybees have internal states such as emotions. Insects do not have the facial muscles used to convey emotions as mammals do.
The researchers set out to see if there were emotions in response to food. They gave bumblebees water containing sugar, salt, and quinine, which is bitter, and filmed their reactions with a high-resolution camera. After tasting sugar water, bumblebees repeatedly extended the tongue-like protrusion (glossa) they use to suck nectar from flowers. When tasting salty and bitter flavors, they wiped their mouths and shook their heads.
The researchers said this is the first time that insects have been observed showing liking or disliking toward food. Mammals make faces when eating delicious food, which is considered evidence of an inner world that goes beyond a simple instinct to seek and consume food. Behavior similar to emotion has never been observed outside mammals.
Barron said the bumblebees' subtle facial expressions could be the key to understanding their minds. "There has always been tension over whether to see insects as animals or as a kind of small robot," he said. "This study is another step showing that honeybees also have an inner world."
◇ Even foul-tasting becomes sweet after exercise
The two reactions could simply be seen as different responses to different chemicals rather than emotional signals of pleasure or displeasure. But when bumblebees were exposed to a hot environment with no water to drink, they extended their tongues even when drinking plain or salt water. The same substance elicited different reactions.
The researchers interpreted this as emotions changing according to physical condition. Barron said, "If you give me an electrolyte drink right now, I may find the taste quite nasty, but after finishing a long-distance run, I would think 'this is really the best,'" adding, "An internal state is changing the evaluation of things."
The researchers also said the bumblebees' expressions did not simply stem from a desire to find food. Even when given dopamine, which drives motivation to seek food in mammals, bumblebees did not increase the number of tongue extensions. In contrast, when given endocannabinoids, which increase liking for food in mammals, honeybees increased tongue extensions. This means the emotions indicating appetite and pleasure were different.
Scientists called the study an innovative foray into a difficult topic. Jonathan Birch, a professor at the London School of Economics (LSE), said, "This is the first case where wanting and liking have been distinguished and revealed in honeybees," adding, "A golden age has opened for research that uses modern technology to uncover the behavior of insects that people have underestimated."
Ralph Adolphs, a professor at Caltech, also said, "The evidence presented in the paper shows that honeybees express the value of gustatory stimuli in a flexible way." However, he said it is unclear whether this experiment proves pleasure in the sense we understand it. "Just as an actor can fake a facial expression and people with facial paralysis still feel emotions, the idea that expressions literally constitute emotions is not true," he said.
References
PNAS (2026), DOI: https://doi.org/10.1073/pnas.2529114123