Insects Don’t Feel Pain

“God in His wisdom made the fly / And then forgot to tell us why.” —Ogden Nash, The Fly

In A Nutshell

Emotional and physical pain allow us to learn from our experiences and modify future behavior. Nocireceptors, responsible for the sensation of pain, are not present in insects—whose lifespans are too short for pain to be useful. Since insects lack nocireceptors, they cannot experience pain.

The Whole Bushel

Pain is a complex emotion. It’s our brain’s response to negative stimuli, from a heart-wrenching break-up to a hot stove scalding a hand. This response is delineated into an experience that encourages us to avoid pain in the future—the negative consequences of pain allow us to learn from past behavior.

Pain is useful to higher-order animals with longer lifespans and was likely a contributing factor to the development of those lengthier lives. The ability to learn from a negative experience ensures a greater chance of avoiding threatening stimuli in the future.

It makes sense, then, for insects, whose lifespans are comparatively short, to lack nocireceptors, which are the receptors directly responsible for pain detection. Nocireceptors send signals to the brain that trigger a painful response. As insects lack nocireceptors, or any equivalent, they cannot experience pain (or at least our version of pain). This conclusion extends to all arthropods, which also includes arachnids, crustaceans, and myriapods.

Observations of insects seem to corroborate this idea. A caterpillar or grasshopper will attempt to continue its routine even while being eaten alive or tortured by a toddler. Insects with damaged bodies attempt to operate as usual—no limping or crying.

Since many insects live for only a few days, they have no need to learn from a painful experience. They’ll be dead soon anyway. Insects are bred for pre-programmed robotic actions; they can glean few benefits from learned behavior or emotions of any kind.

But some scientists continue to debate this issue. Though they lack nocireceptors and show a general indifference toward painful stimuli, arthropods still may have a capacity for experiencing pain of some kind—though it is almost certainly not the same type of pain we experience.

For example, an experiment at Queen’s University Belfast examined the response of crabs (crustaceous arthropods) to electric shocks. The crabs demonstrated an aversion to the shock. While some researchers argued that the crabs’ negative response to the shocks was automatic, others suggested that perhaps crabs—and all crustaceans—actually do experience pain.

A similar experiment was conducted by Stanford University involving fruit flies. The flies were exposed to heat probes, to which they showed some measure of aversion. The researchers discovered that a sensory neuron was responsible for the evasion, but were divided over whether the flies were experiencing pain or were responding to the heat probe with preprogrammed reflexes.

These experiments indicate that arthropods may experience some type of basic pain, but a definitive conclusion may never be possible. However, without nocireceptors and the capacity for emotional behavior, insects cannot experience pain the way other animals do.

Show Me The Proof

ScienceBlogs Neurophilosophy: Do insects feel pain?
The Scientist: Do Crustaceans Feel Pain?
Do insects feel pain? A biological review (pdf)

  • edzyl blane

    So all that torture i do when i capture an ant ( like pulling their legs apart, drowning them and finally crushing their bodies) is all like futile?

    • ethan

      y would u do that>? psychopath

  • Hadeskabir

    I didn’t know insects didn’t feel pain. I actually feel better now, I’ll never feel sorry when I kill an insect for now on.

    • Doone00

      “For now on” why don’t you actually read the article?

      • Hadeskabir

        Thank you for your comment kind sir. It was very useful, I beg of you to continue spreading your knowledge.

  • Errkism

    Theoretically couldn’t we take out the nocireceptors in humans to remove pain but keep the ability to feel? This way we wouldn’t experience pain yet we would still know if we hurt ourselves, like stepping on a nail or something. Feel free to explain to me why this would or would not be possible.

    • lbatfish

      Example: It would still hurt to listen to the Jonas Brothers.

    • Hadeskabir

      If we don’t feel pain we’ll start putting ourselves at risk more often. We would do things that would normally cause a lot of pain and put our bodies at risk sometimes causing severe damage to it or even death.

    • Nomsheep

      If you don’t feel pain then there is no real reason for you to avoid repeating that behaviour.

      • Errkism

        Don’t you think there is a middle ground though? For example, we keep enough pain to where it would deter people from repeating the behaviors you are talking about, but take out the ability to feel immense amounts of pain? That would take torture completely out of the picture, which in my opinion is absolutely huge. Because it’s common knowledge torture is used by countries across the world to get answers, but it would also take away a lot of the fear and pain of victims of serial killers. And to my knowledge, which isn’t much, is why a serial killer commits these acts in the first place is to see the pain and discomfort in their victims.

        • Nomsheep

          Maybe, but the fear of pain is what stops us repeating the action.

          It would just remove one kind of torture there are other methods, and only some serial killers do for the pain, they are many reasons that someone kills.

    • CeledonaMargaretteBlanco

      Pain signals us that something is wrong. Pain signals danger and evokes caution. If you take away the human capacity to experience pain, you’ll be putting the human race into extinction. Imagine your entire body is on fire, but you don’t mind it because you don’t feel it. Or you getting shot in the chest but you shrug it off simply because you can’t feel it. In short, millions of people will die every day just because they can’t feel pain and there is no more sense of danger or caution in them… Until everyone has died and there will be no humans in the planet anymore. So you, dear sir, are a certified idiot for even thinking that.

      • Errkism

        I understand the implications of not feeling pain. My point is there probably is a middle ground where we can reduce pain but still have it for its obvious purposes.

  • inconspicuous detective

    yea, i’m actually glad it’s being debated. i’ve been a bug person since i was little, collecting and learning about them for a good while. you can call it automatic reflexes if you like, but humans only gain those after pain. if you grab a spider by the leg and hold it, it may rest there, squeeze and it bites. i’ve been there, done that. they feel some kind of pain, trust me, and they learn from it however briefly they may need to.

  • Kata Pilar

    I just ran across this by chance and I must say that I’m stunned by all the misinformation.

    Both claims on which this article is based are false.

    (1) Most insects do not live “for a few days”. Most of them live up to a year, some of them overwinter; larval stages of some insects last for several years; cicada larvae live underground for as long as 17 years (and that’s why we have 17-year locusts).

    (2) Existence of nociceptors in insects has been shown in many studies (check links below), so neurological base for pain is there. That is no proof of the “feeling” of pain though. Also, even the Eisemann reference (the review) posted here as “proof” debates that it might be not-so-accurate to make conclusions on insect pain by searching for the same structures that mammals have (nociceptors). The bottom line is – there is no clear proof that insects feel pain, BUT there is no proof that they don’t either! Here are two nicely summed up articles:

    If I where an editor, I would surely remove an article like this. But hey, science is cool, and anyone can write on the internetz, yay!