We have long thought of insects as instinctive, thoughtless creatures. A kind of robots that react impulsively to external stimuli. But through a number of interesting studies, we are learning more and more about the complexity of the critters.

For example, bees appear to communicate with each other through dance movements. Ants interact in impressive ways and termites build awesome structures from scratch. New research provides evidence that insects likely experience pain just like us.

nociception

The key word in this research is nociception, or the ability of an organism to perceive tissue damage or impending tissue damage. This can be the pressure that comes with squeezing, a (chemical) burn or a cut. These stimuli can trigger all kinds of physical and behavioral reactions. Feeling pain is one of them.

It is clear that insects can react defensively when attacked. But that doesn’t prove that they experience pain. A 2019 study, in which the fruit fly (Drosophila) under the magnifying glass showed that the critters suffered from chronic pain after amputating a leg. After the fruit fly had fully recovered, the opposite leg appeared to have become extra sensitive.

Pain Relieving Mechanism

The scientists attributed this to a faulty ‘pain-relieving mechanism’ in his nervous system. The idea is that this mechanism alleviates the pain in a healthy fruit fly, but when the leg was removed, the sensory nerves received such a blow that the mechanism broke.

But this is a lot of assumptions. Even a bacterium responds to unfriendly stimuli by running away. Pain stimuli in organisms have not yet been proven. Consciously registering and regulating pain only works if a complex neurological system is linked to a brain. You could say that a pain experience is only real when emotions are involved.

In mammals you can see that the pain receptors (nociceptors) set off an alarm in the brain in the event of unpleasant stimuli. The brain turns this into a negative, physical and emotional pain experience.

fruit fly. Photo: Vasekk / Getty Images

Severely Wounded Soldiers

Research has shown that nociception and pain can exist independently of each other. Clearly distinct mechanisms have been found for regulating these stimuli. This new research identifies these systems in insects. “A clear feature of pain perception in humans is that it can be regulated by nerve signals from the brain,” said neurobiologist Matilda Gibbons of the Queen Mary University in London. “Severely wounded soldiers on the battlefield sometimes don’t realize how badly they are wounded, because the body produces opiates. This suppresses the nociceptive signal.”

Gibbons: “We are looking for a similar mechanism in insects. Does the insect brain fire the same nerve signals, so that we can speak of a pain experience? Or is it just nociception what we see.”

Opium for the bee colony

Gibbons and her colleagues searched the scientific literature and came across more and more evidence confirming the existence of this mechanism in insects. The animals do not have opiate receptors, but they do produce proteins that have the same function.

It seems very likely that insects can fire nerve signals from their brains to other parts of their bodies in order to suppress the annoying stimuli. For example, bees ignore negative stimuli when there is a lot of sugar in the area and a tobacco pintail tends to its own wounds.

Insects come in all shapes and sizes, some more complex than others, so it’s hard to say that all insects feel pain. But the idea that insects experience pain to some degree is thought provoking. Is it ethical what we do with these animals?

Insect rights?

“By 2050, we may be with ten billion people on Earth. Intensive livestock farming is bad for the climate. The United Nations is encouraging the mass production of insects as an alternative food source,” the researchers explain. “But the ethical consequences of this have not been discussed. In animal protection, we never talk about insects. Will this change in the future?”