Insects can feel pain, evidence shows

Insects can feel pain and wonder what it means when at least a billion of them die each year to be used as food for humans and animals. Routine methods of killing include extreme heat and cold, often preceded by starvation. By comparison, “only” around 79 billion mammals and birds are killed each year.

Scholars have long recognized that the survival value of pain means that many animals experience it, presumably with the exception of insects. But we looked at over 300 scientific studies and found evidence that at least some insects feel pain. Meanwhile, other insects have not yet been studied in sufficient detail.

We also conducted our own study on the response of bumblebees to potentially harmful stimuli. The way they reacted to stimuli was similar to pain responses in humans and other animals.

Death of insects by pesticides

Pesticides kill billions of wild insects each year. The true cause of death is usually paralysis, asphyxiation or dissolution of internal organs, sometimes for several days.

If insects feel pain, insect breeding and pest control would cause enormous suffering. However, animal welfare debates and laws almost universally ignore insects. One reason is that historically, insects were often considered too simple with too short a lifespan. But there is growing evidence that insects feel pain.

Do insects feel pain?

The question of whether insects feel pain is difficult to answer. Pain is an inherently private experience. The difficulty of diagnosing pain when the being in question cannot speak is illustrated by the relatively recent treatment of babies during surgery.

As late as the 1980s, many surgeons believed that babies did not feel pain and rarely used anesthetics because they thought that babies’ obvious responses, such as screaming and squirming, were “just reflexes”. Although we still don’t have proof that babies feel pain, most now accept that they almost certainly do.

For any being unable to directly communicate their suffering, we must rely on common sense and probability. The more pain indicators found, the greater the probability. It is important to use consistent criteria across animals and look for the same behavioral indicators of pain in insects that one would use in a cow or dog.

brain pain

Most animals exhibit “nociception”: the processing of noxious stimuli that can result in reflex responses. Scientists have long known that insects exhibit nociception. However, if an animal detects potentially harmful stimuli, it is not necessarily an indicator of the “woe” pain that is generated in the brain in humans. Both nociception and pain can occur, to some extent, independently of each other.

On a recent study, we found that bumblebees’ responses to heat depend on other motivations. We gave the bumblebees four feeders: two heated and two unheated. Each feeder distributed sugar water, which bumblebees love.

When each feeder had the same concentration of sugar water, the bees avoided the two hot feeders. But when the heated feeders dispensed sweeter sugar water than the unheated feeders, the bumblebees generally chose the heated feeders. His love of sugar outweighed his hatred of heat. This suggests that bees feel pain because (like humans) their responses are more than just reflexes.

The bees also remembered hot and non-hot feeders and used this memory to decide which one to feed on. So, compensation happened in the brain.

Insect brains change their behavioral responses to damage in other ways. For example, hungry flies are less likely to jump from extreme heat than satiated flies. Headless flies can still jump, but they don’t show this difference, demonstrating their brain’s involvement in heat prevention. Communication between the brain and the responding body part is also consistent with pain.

Other indicators that insects can feel pain

The framework we used to assess the evidence for pain in different insects was the one that recently led the UK government to recognize pain in two other major groups of invertebrates, decapod crustaceans (including crabs, lobsters and shrimp) and cephalopods (including octopuses). ). and squid). , including them in the Animal Welfare (Sensitivity) Act 2022. The framework has eight criteria, which assess whether an animal’s nervous system can withstand pain (such as brain-body communication) and whether its behavior indicates pain (such as brain-body communication exchange). motivational).

Flies and cockroaches satisfy six of the criteria. According to the framework, this equates to “strong evidence” of pain. Despite weaker evidence in other insects, many still show “substantial evidence” of pain. Bees, wasps and ants meet four criteria, while butterflies, moths, crickets and grasshoppers meet three.

Beetles, the largest group of insects, meet only two criteria. But, like other insects that received low marks, there are very few studies on beetles in this context. We found no evidence of any insect that did not meet all criteria.

Our findings are important because the evidence of pain in insects is roughly equivalent to the evidence of pain in other animals that are already protected under UK law. Octopuses, for example, show very strong signs of pain (seven criteria).

In response, the UK government included octopuses and crabs in the Animal Welfare (Sensitivity) Act 2022, legally recognizing their capacity for pain.

The UK government has set a precedent: strong evidence of pain warrants legal protection. At least some insects meet this standard, so it’s time to protect them. For starters, we recommend including insects in the Animal Welfare (Sensitivity) Act 2022, which would legally recognize their ability to feel pain. But this law only requires the government to consider your welfare when drafting future legislation.

If we want to regulate practices like agriculture and scientific research, the government needs to expand existing laws. For example, the Animal Welfare Act 2006, which makes it a crime to cause “unnecessary suffering” to animals covered by the law. This may lead insect farms, like conventional farms, to minimize animal suffering and use humane killing methods.

The Animals (Scientific Procedures) Act 1986 regulates the use of protected animals in any experimental or scientific procedure that is likely to cause pain, suffering, distress or permanent harm to the animal. Protecting insects under this law, as octopuses already are, would regulate insect research, reducing the number of insects tested and ensuring that experiments have a strong scientific basis.

Finally, pesticides are a major concern for the welfare of wild insects. We recommend developing more humane pesticides that kill insects faster and minimize their suffering.

This article was written by Matilda Gibbons, PhD candidate in behavioral neuroscience at Queen Mary University of London; Andrew Crump, postdoctoral fellow at the London School of Economics and Political Science; and Lars Chittka, Professor of Sensory and Behavioral Ecology at Queen Mary University of London.


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