The sheer scale of insect deaths in our modern world is staggering. Every year, it’s estimated that at least a trillion insects are killed for food production and animal feed. The methods employed are often harsh, including extreme temperatures and starvation. When you compare this to the “mere” 79 billion mammals and birds slaughtered annually for livestock, the numbers are stark. For a long time, conventional scientific and ethical thinking has relegated insects to a different category, assuming they are too simple to experience pain – a sensation deemed crucial for survival and therefore prevalent across much of the animal kingdom, supposedly excluding insects.
However, this long-held assumption is increasingly being challenged. A comprehensive review of over 300 scientific studies reveals accumulating evidence suggesting that at least some insects are indeed capable of feeling pain. For many others, the research is still in its early stages, leaving the question open. Adding to this growing body of evidence, our own research has focused on bumblebees and their reactions to potentially harmful stimuli. The observed responses in these bees mirror pain responses seen in mammals and other animals that we readily accept as sentient beings.
Beyond farming, the widespread use of pesticides contributes to the deaths of trillions more wild insects each year. The ways these chemicals kill are often brutal: paralysis, suffocation, or the slow dissolution of internal organs, sometimes playing out over days. If insects are capable of feeling pain, then these practices, alongside insect farming, raise serious ethical questions about mass suffering. Yet, remarkably, discussions and laws surrounding animal welfare almost universally ignore insects. Historically, this neglect stems from the perception of insects as simplistic creatures with fleeting lifespans. But the rising tide of evidence for insect pain demands a re-evaluation of this perspective.
The question “Does Fly Feel Pain?” or indeed, whether any insect feels pain, is complex. Pain is subjective; it’s an internal experience. Diagnosing pain in any being that cannot verbally communicate is inherently difficult. Consider the historical treatment of human babies during surgery. As recently as the 1980s, a disturbing number of surgeons operated on infants with minimal or no anesthesia. The rationale? A misguided belief that babies were incapable of feeling pain, their cries and movements dismissed as mere reflexes. Even without definitive “proof” that babies feel pain, the overwhelming consensus now rightly assumes their sentience.
When dealing with any creature unable to articulate suffering, we must rely on a combination of scientific observation, logical inference, and common sense. The more indicators of pain we observe, the higher the probability of its existence. Consistency is key: we need to apply the same criteria for assessing pain in insects as we would for a cow or a dog.
Deciphering Pain in the Insect Brain
A crucial distinction in this discussion is the difference between nociception and pain. Nociception is the nervous system’s detection of harmful stimuli, triggering reflex responses. It’s well-established that insects exhibit nociception. However, simply detecting a potentially damaging stimulus doesn’t automatically equate to feeling “ouch-like” pain, which, in humans, is a brain-generated experience. Nociception and pain can, to some extent, operate independently.
Our recent study delved deeper into bumblebees’ responses to heat, revealing that these responses are not merely reflexive but are modulated by other motivations, suggesting a more complex processing consistent with pain. We designed an experiment with bumblebees and four feeders: two heated and two unheated, all dispensing sugar water, a favorite bee food.
Alt text: A bumblebee in flight, illustrating research into insect responses to stimuli and the question of whether insects feel pain.
Initially, when all feeders offered the same sugar concentration, the bees understandably avoided the heated feeders. However, when we increased the sugar concentration in the heated feeders, making it sweeter than the unheated options, the bees’ behavior shifted dramatically. They frequently chose the heated feeders, demonstrating that their preference for sugar could override their aversion to heat. This is a key indicator of pain, as it suggests that, like humans, bees make complex decisions that go beyond simple reflexes, weighing different motivations against a potentially painful stimulus. Further solidifying this, the bees demonstrated memory of which feeders were heated and unheated, using this information to guide their future feeding choices. This decision-making process clearly occurs in the brain, pointing towards a centralized processing of the heat stimulus as something more than just a reflex.
This brain-mediated modulation of responses to harm is not unique to bees. Studies on flies have shown similar complexities. For instance, hungry flies are less likely to jump away from extreme heat compared to flies that are satiated. Intriguingly, decapitated flies, while still capable of jumping (a reflex action), do not exhibit this difference in heat avoidance based on hunger. This strongly implicates the brain in processing and modulating the response to potentially harmful heat, moving beyond a simple reflexive action and aligning with the experience of pain. The communication between the brain and the body’s response further strengthens the argument for a pain-like experience in insects.
Pain Indicators and the Ethical Implications
The framework we employed to evaluate the evidence for pain in insects is the same rigorous framework that recently led the UK government to recognize sentience in decapod crustaceans (crabs, lobsters, prawns) and cephalopods (octopuses, squid). This framework, underpinning the Animal Welfare (Sentience) Act 2022, uses eight criteria to assess both the neurological capacity for pain (like brain-body communication) and behavioral indicators of pain (such as motivational trade-offs).
Applying this framework, flies and cockroaches satisfy six out of the eight criteria. According to the framework’s guidelines, this constitutes “strong evidence” for pain. While the evidence is less conclusive for some other insect groups, many still show “substantial evidence.” Bees, wasps, and ants meet four criteria, while butterflies, moths, crickets, and grasshoppers fulfill three. Beetles, the most diverse insect group, currently only satisfy two criteria. However, it’s crucial to note that for beetles, and many other lower-scoring insects, research in this specific context is severely lacking. Importantly, our review found no evidence of any insect failing to meet any of the criteria.
These findings have significant implications. The level of evidence for pain in insects is comparable to that for other animals already afforded legal protection in the UK. Octopuses, for example, exhibit very strong evidence for pain, satisfying seven criteria within the framework. In response to this evidence, the UK government included both octopuses and crabs in the Animal Welfare (Sentience) Act 2022, legally acknowledging their capacity to experience pain.
The UK government’s precedent is clear: strong evidence of pain justifies legal protection. Given that at least some insects meet this standard, it’s time to extend similar protections to them. A crucial first step would be including insects under the Animal Welfare (Sentience) Act 2022, formally recognizing their capacity for pain in law. While this act mandates government consideration of their welfare in future legislation, further action is needed to enact real change.
To effectively regulate practices like insect farming and scientific research involving insects, existing animal welfare laws need to be expanded. For instance, the Animal Welfare Act 2006, which criminalizes causing “unnecessary suffering” to protected animals, could be extended to include insects. This could drive the insect farming industry towards minimizing suffering and adopting humane slaughter methods, mirroring practices in conventional livestock farming. Similarly, the Animals (Scientific Procedures) Act 1986, regulating the use of protected animals in potentially harmful scientific procedures, could be amended to include insects, as it already does for octopuses. This would regulate insect research, reduce the number of insects used in experiments, and ensure robust scientific justification for any research that could cause suffering.
Finally, the welfare of wild insects in the face of widespread pesticide use must be addressed. Developing more humane pesticides that kill insects more rapidly and minimize their suffering should be a priority. The growing body of evidence suggests it’s time to broaden our circle of compassion to include these often-overlooked creatures and reconsider our ethical responsibilities towards the insect world.
