Tiny in size but fierce in defense, harvester ants (Pogonomyrmex spp.) pack a sting that will knock your socks off. Particularly effective against mammals, harvester ants’ venom may have evolved to keep rodents from raiding their seed stashes. The pain from a sting to a human can last several hours—an impressive power for such a small insect. Shown here is a western harvester ant (Pogonomyrmex occidentalis). (Photo by Derek Uhey, Ph.D.)

By Derek Uhey, Ph.D.

Derek Uhey, Ph.D.

Tiny in size but fierce in defense, harvester ants (Pogonomyrmex spp.) pack a sting that will knock your socks off. What starts as a sharp pinch quickly escalates into a small fire within your skin. This is no mere ant “bite”—this is envenomation, and far more powerful than a mild honey bee sting. After the pain subsides, you may wonder about the incredible arsenal of these ants.

Harvester ants are common across arid regions of North America, with some species building large, conspicuous nests where they store plant seeds. It’s these species that possess the most powerful stings. It’s hypothesized that harvester ants evolved their stings to keep rodents from raiding their seed stashes. Their stings seem to be especially effective against mammals. So, next time you are stung, think of yourself as unfortunate collateral damage in the evolutionary arms race between ants and rodents.

What does a harvester ant sting feel like? I’ve experienced hundreds in my lifetime. Many factors determine the severity, such as which harvester ant species, their venom load, and your own sensitivity. Most important, though, is sting location. Harvester ants have a hard time stinging through thick skin. I have callused fingertips from guitar playing and commonly pick up harvester ants between my fingers without getting stung. A sting on the calf or forearm is usually no big deal.

However, get stung somewhere sensitive, and it’s shocking. My worst sting was in a vein on my foot. I had been researching ant hills in the desert when one had crept into my shoe and stung me through my sock as I was driving home. I had to pull over on the side of the highway to let the pain subside. The pain usually peaks in about 20 to 30 minutes, but it can last over eight hours. Besides pain, common side effects are redness, swelling, goosebumps, and sweating. Often, the skin hardens into a red welt that stays itchy and irritated for a few days.

Tiny in size but fierce in defense, harvester ants (Pogonomyrmex spp.) pack a sting that will knock your socks off. The pain can last several hours and leave a red welt (such as shown here, on the inside of an elbow) that stays itchy and irritated for a few days. (Photo by Derek Uhey, Ph.D.)

Justin Schmidt is famous for his dissertation work categorizing hymenopteran stings, which he first conceptualized after getting stung by a harvester ant. He classified stings on a pain scale ranging from 1 to 4. Harvester ant stings earned a 3, described by Schmidt as “After eight unrelenting hours of drilling into that ingrown toenail, you find the drill wedged into the toe.” Similar ratings are assigned to yellowjackets and paper wasps. In the desert southwest, only tarantula hawk wasp stings, at level 4, outrank those of harvester ants.

Schmidt’s research went far beyond categorizing sting pain; he also explored the venom biochemistry. Harvester ant venom is composed mostly of specialized peptides that profoundly alter sodium ion channels used in mammalian nervous systems. Schmidt found one species, the Maricopa harvester ant (Pogonomyrmex maricopa), to possess the most toxic venom known for insects. The lethal dose for 50 percent of a population (LD₅₀) in mice was just 0.12 milligrams per kilogram. That’s about 12 stings to kill a 2 kg rodent. Don’t worry, though—this equates to hundreds to thousands of stings for a full-grown human!

Long before European settlers learned of harvester ant stings, Indigenous peoples used them for a variety of cultural and therapeutic purposes. These practices were especially prevalent among Shoshonean-speaking tribes of south-central California. Ants were either allowed to sting externally or swallowed alive to treat a variety of ailments such as severe colds, pain, arthritis, and gynecological disorders. These treatments were reported by early ethnobiologists as highly effective, but much of this traditional knowledge may be lost or kept secret. To be clear: Purposely stinging yourself with any hymenopteran is extremely risky, as you never know if you’ll have an allergic reaction, so do not try this at home!

Tiny in size but fierce in defense, harvester ants, such as the western harvester ant (Pogonomyrmex occidentalis) shown here, pack a sting that will knock your socks off. Particularly effective against mammals, harvester ants’ venom may have evolved to keep rodents from raiding their seed stashes. (Photo by Derek Uhey, Ph.D.)

Particularly interesting is the ritualistic swallowing of harvester ants to induce visions, similar to peyote and datura use. Individuals wishing to acquire supernatural power in the forms of “dream helpers” would swallow hundreds of live, stinging ants. This produces a catatonic hallucinogenic state in which animal or ancestral spirits are believed to confer virtues on the seeker. These virtues may include the ability to cure illnesses, bewitch others, or be immune to venomous creatures—some nice virtues for those who have the stamina to risk death from ant stings.

Before ritualistic ant swallowing, Indigenous peoples would follow careful dietary and spiritual guidelines, which they believed were necessary to avoid dying from the ant venom. As far as outsiders can tell, ritualistic ant swallowing seems to have ceased following European colonization in North America. Again, it is important to be clear here that swallowing live, stinging ants is not only painful, but extremely dangerous. In other words, I don’t recommend using harvester ants to enhance your next music festival experience!

Thankfully, harvester ant stings are a rare and fleeting experience for most of us. Harvester ants are not particularly agile and tend to stay relatively close to their nests, so with a little care, you can easily avoid them. Harvester ants are native and beneficial here in the United States, arguably keystone species in desert ecosystems. While you won’t forget a harvester ant sting, you’ll likely quickly recover, and maybe you can then marvel at how such a tiny ant can bring about such pain.

Derek Uhey, Ph.D., is an assistant teaching professor in the School of Forestry at Northern Arizona University in Flagstaff, Arizona. Email: [email protected].