THE STINGING POWER OF BULLET ANTS did not go unnoticed by local people. Various indigenous peoples in northern Amazonas traditionally used and some continue to use the ants in ceremonial rites of manhood. The Ararandeuara used a ceremonial braided fiber cylinder about 60 cm long and 20 cm in diameter, closed at each end with a drawstring. The cylindrical muff was filled with bullet ants, the desirous youth then placed his hand in the mitt, and the drawstrings were snugged around his forearm. If he could keep his hand inside the mitt for a length of time, withstanding the pain, he was proclaimed a man fit to marry and the celebrations continued.2 This procedure adds perspective to the old adage “no pain, no gain.”
Several variants of puberty rites have been reported among the Amazon peoples. In Suriname, woven mats are fashioned to hold bullet ants by the constriction between the ants’ thorax and abdomen, thereby preventing ant escape. The mats are then charged with bullet ants having their business ends all facing one side. The mat is placed on the candidate boy’s abdomen, gluteus maximus, thighs, and so forth, where they readily sting. After withstanding this treatment “like a man,” the boy is fed an herbal concoction and rests in a hammock, while the rest of the tribe has a long celebration of his manhood.23 Another version of the ceremony was recorded on video in the PBS Nature series titled “Gremlins: Faces in the Forest,” produced in 1997. The main emphasis was discovering and recording the tiny and reclusive marmoset and tamarin monkeys of the Amazon forest. In the process of their discoveries, they recorded “as filler” the use of bullet ants in a manhood ritual. In that version, the boy was first painted black before the ants were applied. Several YouTube clips have appeared subsequent to that 1997 “Gremlins” recording. These included a ceremony featuring a Satery boy during initiation rites (http://www.youtube.com/watch?v=XwvIFO9srUw). His dedication and mental strength make the ceremony appear perfunctory and the stings only a minor pain. Another view narrated in Portuguese (http://www.youtube.com/watch?v=gjna7MnPKrI) reveals a greater impact of the pain. Hamish and Andy provide an ultimate contrast in human response to the sting pain; in this case, by a person not so dedicated to passing an initiation test (http://www.youtube.com/watch?v=it0V7xv9qu0&list=RDit0V7xv9qu0&index=1). Several hundred thousand viewings of these ceremonies suggest a great underlying appeal and popularity of bullet ants to people, no matter where they live.
The Ka’apor of Amazonas use another large ant, the termite predator Neoponera commutata, in puberty rites for girls. The stings of these ants are painful, but not nearly as painful as those of bullet ants; hence, their choice for girls. William Balée of Tulane University described these rites in detail, along with several others involving bullet ants and other ants.24
The Amazon people appreciated the toxicity of bullet ants. Some tribes in the far upriver reaches of the Amazon mixed bullet ant venom with other toxic ingredients to produce the arrow poison curare, locally known as woorali, which is deadly if introduced under the skin, but harmless when ingested.2 My suspicion is that the painless curare alkaloids were the true paralytic/lethal components and the bullet ant venom contributed the painful part of the poison. What tribal peoples knew for certain was the painfulness of bullet ant stings and venom.
The culprit that ties together all the stories about bullet ants is the venom. Bullet ant venom is as unique and unusual as the ants themselves. The venom is highly lethal to mammals, having a lethality of 1.4 mg venom per kilogram body weight, and is produced in the prodigious quantity of 250 micrograms per average ant.25 The two combine to yield a projected capacity for one sting to kill a mammal of 180 grams, about the size of a young female Norway rat. This killing power is over three times that of a honey bee and nearly eight times that of a baldfaced hornet. In contrast to the venom’s killing power is its amazingly low ability to destroy cell membranes and tissues. Among the 10 ants tested, bullet ant venom came in dead last in ability to destroy red blood cells, a standard assay for tissue damage. Its activity was so low that it was 48-fold lower than harvester ant venom and a whopping 1,200 times less active than the Brazilian paper wasp, Polistes infuscatus.26 This low membrane and tissue damage potential explains the typical human sting reaction of little swelling or redness and trivial signs of the sting after the pain recedes.
Two questions spring to mind: (1) What makes the venom so painful? (2) What makes the venom so lethal? The venom contains small amounts of kinins, much like those abundant in social wasps, but these are minor factors in the overall activity and do not produce redness or swelling, which occurs with wasp stings. The more interesting factor is a 25 amino acid peptide called poneratoxin. Poneratoxin is four times more lethal than whole venom and accounts for most of the venom’s lethality. This acidic peptide is also highly active at concentrations as low as 25 µg in a liter volume, causing long-lasting contraction of smooth muscles in the body, undulating changes and bursts of transmitter release in nerves and muscles, blockage of cockroach nerve signal transmission, and impeding sodium channels of skeletal muscles.27 These activities explain most, if not all, activities observed in the field. As a final check on the activity of poneratoxin, I injected a tiny amount of synthetic poneratoxin provided by my collaborator Steve Johnson under my forearm skin to make a small bleb about a tenth the size of the bleb produced in a TB test. The reaction and pain were identical to that of a real sting but, fortunately, less severe than a true sting because only a small amount of venom was injected. (I wanted answers, but not serious pain; that’s why the dose was small.) The dose was too small to cause muscle trembling, something predicted for poneratoxin, though it did induce the urge to shake the arm. This forearm test suggests that most, perhaps all, of the sting pain and reaction is caused by poneratoxin, though other causative factors could also be present. No other ant, or other venomous animal, contains a peptide similar to poneratoxin. It is a truly unique toxin from a truly unique ant.
The superlative nature of this ant and its venom brings to mind the question, Why? Why does this species need such a potent venom? Why don’t other ants (or other stinging insects) have similar venoms? These questions cannot be answered directly, but we can get hints about the forces operating on the ant that selected for its venom. These forces, primarily from large vertebrate predators, operate to a lesser degree on many other stinging social insects. Why only bullet ants evolved poneratoxin but not other ants, wasps, or bees is part taxonomic lineage and part randomness. Once a trait evolves in a lineage, descendant species of that lineage can easily maintain or genetically modify that trait. Neither bees, wasps, nor other ants had anything similar to poneratoxin in their lineage, so evolution of a poneratoxin-like molecule would have to be de novo, a much more difficult evolutionary process. The bullet ant lineage separated from those of other ants around 100 million years ago. This provided bullet ants a hundred million years alone to evolve poneratoxin, something they obviously did, perhaps by random mutation.
Back to the forces that would select for poneratoxin. In rainforests, most vertebrate predators, whether mammals, birds, lizards, or frogs, live in the forest canopy. Relatively few live on the dark forest floor or on dim low understory plants. Part of the reason vertebrates are active in the canopy is that most leaves, flowers, fruits, and insects are present in the canopy. To get these resources, a species must go to, or be in, the canopy. However, for an insect, the canopy is a dangerous place where you are almost as likely to become dinner as find dinner. The insects in the canopy are generally hidden in retreats much of the time or are camouflaged, cryptic, behaviorally secretive, temporally ephemeral, or otherwise out of view. The alternative is to be bright, flashy, and very nasty. Bullet ants nest in the relatively safe ground environment but must forage in the canopy for food. They are big, conspicuous, and long-lived, all factors working against survival among hordes of hungry birds, monkeys, lizards, and amphibians. What bird or monkey would not like a nice big, juicy insect for a snack? Bullet ants cannot jump or fly away to escape, and they cannot easily hide, so they m
ust face the predators. This they achieve better than any other stinging insect through their venom. If a predator is unwary enough to grab a bullet ant, it likely will remember the experience and not repeat it. To aid in warning predators to look elsewhere for food, bullet ants have several aposematic signals. First, they are shiny and blackish, a common indication of inedibility. Second, they loudly stridulate, producing a sound warning to anyone nearby that they are present and not to be messed with. Third, they produce 4-methyl-3-heptanone and other chemicals warning want-to-be predators to be wary and avoid them. In addition to these three warnings are undoubtedly more behavioral traits that signal that they are bullet ants. Some predators are tough, as the toads mentioned earlier; some predators are smart, as are monkeys, and learn tricks to overcome prey. All these predators are in the canopy. To forage day and night in the canopy, bullet ants need serious protection, and their sting is the best there is.
I am often asked how I know bullet ants are the most painful of any stinging insect. Of course, this can never be answered with 100 percent certainty, as thousands of stinging insects have been described, with more awaiting discovery. Neither I, nor anyone else, have been stung by all of them. I have searched six continents (skipping Antarctica) over 40 years for stinging insects and never found any whose stings come even close to the pain level and duration of bullet ant stings. This is not from lack of specific search. In South Africa, I tracked down the feared matabele ant (Megaponera analis), the giant stink ant (Paltothyreus tarsata), and others and found their stings mild compared to bullet ant stings. In Australia, the bull ants in the genus Myrmecia are believed to have horrific stings. Yet, when I and others were stung by bull ants, the pain did not equal that of a honey bee, much less that of a bullet ant. The famed bull-horn acacia ants (Pseudomyrmex) hurt, but again, much less than bullet ants. Tarantula hawk stings hurt as much for a couple of minutes as bullet ant stings, but then vanish, something all of us wish would happen with bullet ant stings. There are reports of extremely painful stinging ants in the Congo and wasps and ants in the western Amazon basin, but the low number of these specific reports and their infrequent or nonexistent confirmation suggest they, too, would be less painful than bullet ant stings. Reports of bullet ant stings almost universally expound the painfulness of the stings. I am confident that bullet ants are the holy grail of stinging insects and deliver the most painful sting of any stinging insect on Earth.
Have I ever intentionally stung myself with a bullet ant? Of course not. No need to. Bullet ants are all too ready to oblige. Mess with a colony, and you will likely be stung. Innocent in the rainforest? Watch out. A hand on a sapling, liana, or tree buttress is asking to be stung by an unnoticed bullet ant. Experienced people learn to look before leaning and, in general, not to grab or hold anything unless it is necessary. The slouch leaning on a fencepost or a tree trunk will quickly stand up straight.
My first experience with the famous tucandéra, as bullet ants are called in Brazil, occurred in the delightful city of Belém at the mouth of the Amazon River. I was with my professor, the colorful, talented Murray Blum, and colleague Bill Overal of the Emilio Goeldi Museum. We were in an older second-growth forest with a goal to collect as many ants and wasps, especially the stinging kind, as possible. We wanted them for comparative studies of pheromones and venoms. We had along an able-bodied assistant named Romero. Romero was the kind of guy you want on your team: big, strong, and afraid of nothing (or so I thought). Find a fire ant colony. No problem. Romero would grab handfuls of dirt with ants, stuff them in a plastic bag, and brush off any remaining ants. Find a social wasp nest in a bush. No problem. Romero would grab it and stuff it in another bag and then slap away those wasps chasing him. We found Dinoponera, those gentle giants of the ant world and the largest ants on earth, and allowed them to crawl on our hands and faces. We then found a bullet ant colony at the base of a sapling. Just what was wanted. They were too large to suck into my aspirator, so I was collecting them one by one with long, 12-inch forceps. That was difficult. Bullet ants are remarkably quick, strong, and agile. And they are sticky, clinging amazingly well to polished chrome forceps as they move ever closer to fingers. I managed to collect all the individuals around the entrance without getting stung, but as daylight was ending I still wanted a lot more before having to leave for dinner. Hurried digging with my pathetic trowel wasn’t working. “Romero, I need help cutting these roots with your mattock. Where is Romero?” Turned out Romero (and Bill and Murray) were safely at a distance watching. “Romero, I need help!” Romero charged in, took a few whacks at the roots, and retreated. Time was getting short, light was fading, and ants were boiling out. No choice, forceps weren’t working well. Grab an ant and with lightning speed toss it into the talcum-powdered, escape-proof jar and repeat. Only bullet ants are lightning fast, too. I can’t remember exactly how many stings I got, four I think, but they were absolutely excruciatingly painful and debilitating. Enough ants—out of here! Bill knew a local churrascaria, one of the Brazilian restaurants that specialize in dozens of different types of meat, many stuck on long swords, that are brought to your table. As we drove to the restaurant my hand was throbbing, sending crescendos of pain, followed by easing a bit, only to be repeated with renewed ferocity. All the while the forearm was uncontrollably vibrating up and down. “Stop it, damn it!” No matter how hard I tried, I could not stop that hand and arm from trembling (the other arm was fine). When I touched the skin around the main sting, it felt numb. Even when I poked the area with a pencil point, I detected no sensation. If poked hard enough, I sensed a dull, deep visceral pain, but nothing else.
When we arrived at the churrascaria, my first request was ice. My second request was a beer. Ice did actually arrest most of the pain, and the beer provided a lift in spirits. Another beer later, it seemed time to stop the ice. Good food was on the table and eating with an iced hand was difficult. As the cold wore off, the pain resumed unabated. It seemed as if I had only delayed the clock, the pain was going to get its time no matter what. Ice back on. Dinner finished and time to relax and plan for the next day. The pain was still there. Bedtime. The pain was still there. Getting to sleep was difficult, but finally came around midnight in spite of the pain. The next morning the pain was finally gone, and if to add insult, little sign I had ever been stung was revealed. Another encounter with bullet ants shows just how effectively they can defend themselves. We were in Costa Rica excavating a bullet ant colony. This time there was no haste and neither of us was interested in being stung. Meticulous excavation yielded many ants and no stings; that is, until an ant fell from the liana above, bounced off my cheek, and landed on the ground. In the process of bouncing, it managed to sting my cheek. The sting was minor, given the little time to inject venom, but it was still a sting. Bullet ants are quick, something we humans are quick to learn through experience.
11
HONEY BEES AND HUMANS
AN EVOLUTIONARY SYMBIOSIS
Apis dorsata is the most ferocious stinging insect on earth.
—Roger Morse, “Apis dorsata in the Philippines,” 1969
BABY TOYS, ELEPHANTS, yellow rain, and Apis dorsata. What do they have in common? They all are connected to honey bees, or they are honey bees. Humanity has no greater a mixed relationship with any animal than with the honey bee. Honey bees are prominently featured in several major religions and are the state emblem and insect of Utah. Israel is the Land of Milk and Honey. Ah, honey. That gives us a clue. Honey bees produce honey and people love honey. Therefore, people love honey bees. But wait. Honey bees sting! That is the crux of our tormented relationship with honey bees. We love their honey, and we love them because they make honey. Yet, they sting, and we are afraid of their stings. The two combined make honey bees most fascinating insects and the second-most scientifically studied of all insects (only the fruit fly, Drosophila, that “white rat” of the insect world, has been the subject of more publications).
My own life with honey bees st
arted at an early age—the exact age I cannot remember. I discovered that I had a talent for picking up honey bees from clover flowers without getting stung. Although I somehow knew honey bees could sting, I do not recall ever being stung; however, my teacher had quite a different experience. I did not remember the incident on the playground in which I placed a honey bee on her arm, but my teacher and mother remembered it and regaled me with it many times during my school years. It turned out that my mother and the teacher were friends.
My first memory of a sting was not from a honey bee but from a bumble bee. Bumble bees, like honey bees, are beloved insects whose motifs adorn infant clothes and toys. One of the reasons they are beloved is that they, with their soft yellow and black rounded furry bodies, are cuter than honey bees. Who doesn’t remember seeing bumble bees playfully visiting one flower in the yard and then the next? Bumble bees also tend not to be aggressive like honey bees. That is, unless one messes with their nest. Then, like any good parents, they tend to defend the home and their young. Mess with their nest is exactly what I did. I was five years old, and our backyard had a low pile of wood in a corner. I saw bumble bees entering and leaving from deep within the woodpile and decided to investigate where they were going. The memory of how I disturbed the bumble bees is lost, but I remember the consequences clearly. Bees came out and attacked. One bee managed to attach itself to the back of my neck and sting me. I screamed and ran toward the back door, swatting at the bee on my neck as I ran. Unlike honey bees that sting only once and lose their stinger in the process, bumble bees do not lose their stingers and can sting many times. That day I received five stings to the back of my neck by that one bee. After that, I never messed with the bumble bees in the yard again.
The Sting of the Wild Page 22