The Worst Pain Known to Man... It's a Stinger

A man stands ready, nervous but staunch. His face and hands are painted in warrior colors – black and red. Today, he will become a man. His initiation will be pain – pure, intense, brilliant pain. Walking over flaming charcoal with a nail in his heel pain.

But his pain won’t come from fire, nor from a rusty nail. It won’t come from being attacked by a bull, a lion, or any other large, fierce creature. It won’t come from hunger or heat.

It will come from… an ant.

They say this is the worst pain known to man. That might not be true, but it’s certainly close to if not the worst pain known to man from an insect. The insect, of the order Hymenoptera, is an ant, the “bullet ant” or Paraponera clavata. Why is this ant called a bullet ant? Because the feeling of being stung supposedly simulates the pain of being pierced by a bullet.

The Satere-Mawe people from the Amazonian basin of Brazil use bullet ants in a rite of passage ritual for manhood and social status, in which young men must place their hands in giant, woven-basket-like gloves filled with a hundred or more of these inch-long ants. The bullet ant’s sting is believed to not only turn the boy into a man, but to give the young hunter better sight for his prey. The bullet ants are rather gruesomely sedated with an herbal brew before being woven, stingers up, into the palm leaves that form the gloves. No wonder these ants sting, over and over, any hand placed into the glove where they are captured, while in the video below, a single ant is seen being quite docile walking across a man’s arm. In fact, bullet ants are typically not aggressive unless provoked.

The Satere-Mawe men, and tourists who think they can withstand the ritual on camera, wear the gloves for up to ten minutes at a time, dancing and singing in a line with other men in an effort to meditate the pain away. But even when the gloves come off, the glove-wearer endures hours of pain-waves from the toxins delivered by the ant stings.

The Satere-Mawe tribe calls the bullet ant tocandira.

"The moment in which one is stung, however, is not the most painful part of the experience. My partner, who has since been bitten several times by bullet ants while working in the Peruvian Amazon, reports that it is the pain that comes after the sting that is truly memorable. He says: 'The pain grows and throbs. It lasts for hours. The area around the wound swells.'" - Mrinalini Erkenswick Watsa, an account from the Peruvian Amazon, SurroundScience

According to one paper published in Chemical Biology of the Topics in 2011, entomologists have described over 950,000 insects. But of those species, one stands above the rest in infamy for the pain it induces – the bullet ant. Alex Wild, entomologist and insect photographer extraordinaire, describes the bullet ant's sting thus: "A great many people will tell you they've been stung by a bullet ant and it wasn’t that bad. Don't believe them – bullet ants are so infamous that people misidentify all sorts of other common large ants as bullet ants. It's a sort of confirmation bias. True bullet ants are quite shocking in size at first appearance. They look like toy ants that have come to life, as though they were molded from plastic."

But being the scientist I am, I’m not satisfied knowing that the bullet ant, Paraponera clavata, has the most painful sting of any other insect in the world. Now I want to know why. What makes the bullet ant’s sting hurt so? What makes the pain of the sting last for hours, up to 24 hours according to some reports?

The answer lies in a neurotoxic protein produced by the bullet ant, called poneratoxin.

Ants are known to use a variety of small molecules in self-defense, including formic acid (also in the venom of bee stings) and various alkaloids. You might be familiar with the physiological effects of some alkaloids already, including morphine, ephedrine and nicotine. An alkaloid called solenopsin causes the pain associated with the sting of the red imported fire ant, for example.

But insect stings that deliver formic acid and various alkaloids are but a candle to the fire of a bullet ant sting. The bullet ant’s poneratoxin is a small peptide (25 amino acid residues long) neurotoxin that can cause extreme pain, cold sweats, nausea, vomiting and even abnormal heart rhythms.

Poneratoxin interferes with the proper function of sodium ion channels known to be important in the function of cells that control muscle fibers, for example. The toxin essentially interferes with nerve cells’ ability to send electrical signals back and forth. The toxin has been shown to prolong action potentials in frog skeletal muscle fibers. And when you mess with nerves and nerve cells – well, you get pain. Or paralysis. In fact, a fine line exists between pain and numbness in the disturbance of nerve cell function. Think of it like when your leg falls asleep – it may be numb and yet feel like “pins and needles” within a short period of time.

The amino acid sequence of poneratoxin looks like this: FLPLLILGSLLMTPPVIQAIHDAQR. Yep, that is the sequence of pain. According to Mario Sergio Palma, the venoms of the social Hymenoptera insects, including poneratoxin, evolved as defensive tools to protect the colonies from the attacks of predators. Other more solitary insects evolved venoms in order to cause paralysis in their prey.

The interesting thing is that sodium ion channel blockers, similar in function to poneratoxin, actually have therapeutic uses in humans. Sodium ion channel blockers have been used in the therapy of epilepsy and as topical anesthetics. In rats, low levels of a synthetic poneratoxin peptide have actually been shown to have pain-blocking properties. Researchers have suggested that we may be able to adapt the bullet ant’s poneratoxin to serve as a painkiller.

So the bullet ant’s toxin not only produces intense pain – the greatest produced by any stinging insect – but it may also under the right conditions block the sensation of pain. How ironic.

But I wouldn’t go trying to get stung by a bullet ant when you have a headache. Your headache might go away, but the pain in your hands likely won’t be worth it.

For a great guide on identifying the bullet ant in the field, see Alex Wild's blog post here. For more images of bullet ants, visit Alex Wild's photography page here.

Paraponera clavata – museum specimen. Dorsal side Locality: Petit Saut, French Guiana, France. From Wiki.