Bees ‘facial expressions’ may be a sign of their inner lives
Skip to content
Cwyn Solvi
https://theconversation.com/bees-facial-expressions-may-be-a-sign-of-their-inner-lives-286839
https://theconversation.com/bees-facial-expressions-may-be-a-sign-of-their-inner-lives-286839
Link copied
Share article
Share article
Copy link
Bluesky
Messenger
X (Twitter)
Print article
It’s easy for us to tell if someone is enjoying their meal or not. They lick their lips if they like it, grimace if they don’t.
Our new research, published today in Proceedings of the National Academy of Sciences, shows we might be able to read insects’ facial expressions in a similar way.
This offers potential insights into their inner lives – and builds on a wave of new work that is daring to suggest insects might have a form of consciousness.
An idea dating back to Darwin
Humans read each other’s expressions and body language all the time. By doing so, we can typically get a pretty accurate read on what another person is feeling.
Naturalist Charles Darwin was one of the first to discuss how facial expressions in other animals might also give us a read of their emotions.
Most dog owners would agree that dogs can communicate clearly through body language and expression when they are joyful, afraid or in pain. In mammals, at least, basic features of facial expressions associated with liking and wanting seem to be deeply conserved through evolution.
Psychologist and neuroscientist Kent Berridge and his colleagues pointed out just how eerily similar the facial expressions of newborn baby humans and baby rats are when they receive a surprising sweet treat versus a bitter one. In both species the former triggered lip licking, whereas the latter triggered a mouth gape of revulsion.
Based on a combination of careful neurobiological and behavioural studies, Berridge has convincingly argued that we can use facial expressions to read what a rat likes and dislikes, and he has used this as a measure to understand the neurobiology of liking in rats.
What about other animals with radically different brains, bodies and faces? What about, say, insects?
Getting a read on an insect’s inner life
Insects have a hard exoskeleton. Their faces are impassive masks, but bumblebees do have highly mobile mouth parts. They can extend their long glossa (the equivalent of a tongue) to reach deep into flowers to sip nectar.
In experiments performed at Southern Medical University in Guangzhou, China, colleagues and I studied how bumblebees moved their glossa and other mouth parts when sampling different tastes.
To a single bumblebee we offered a tiny droplet of sugar water from a pipette. The bee vigorously extended her glossa to drink the droplet, but even after she finished drinking and the pipette was taken away she kept extending and retracting her glossa into thin air – almost as if smacking her lips.
By stark contrast, when we offered the bee a droplet of dilute salty water she sampled it with her glossa, then backed away shaking her head and wiping her glossa as if in disgust.
Testing alternative explanations
Could these responses be simply innate reactions of the glossa to the different chemistry of sugar and salt?
To test this we changed the bee’s physiological state. We heated the bee to 40°C for a short time. While this didn’t harm the bee, it was equivalent to the bee being active on a hot day and caused her to become dehydrated.
Now when we offered the bee dilute salty water, rather than shaking her head and wiping her mouth, she drank thirstily and showed those glossa extensions.
This showed the glossa movements were not automatic responses to sugar and salt. Rather they had more to do with the bees’ physiological state. A dehydrated bee needs dilute salty water, and now when offered it she showed the glossa extension responses she would otherwise show to sweet sugar.
It’s somewhat like those oral rehydration electrolyte drinks. Most of the time they are bearable – just. But if you have just completed a long run and are dehydrated, they taste so much better.
In other experiments we directly manipulated the bees’ neurochemistry.
We found that if we treated bees with different neurochemicals we could change the glossa response to sugar. Bees treated with the neuromodulators octopamine and dopamine were more reactive to sugar, but did not show those post-drinking glossa protrusions to a sucrose drop.
However, bees treated with an endocannabinoid (a different neuromodulatory system that in mammals is related to mood, appetite and physiological regulation) showed enhanced post-drinking glossa protrusions, but were not more reactive to sugar.
This told us two things. First, the glossa protrusion is independent from a sugar reaction. Second, very specific changes in bee neurochemistry can enhance the glossa protrusion response.
A subjective inner state
Together these experiments showed that...