The Sting of the Wild

by Justin O. Schmidt

  I am often asked how one can distinguish fire ants from other ants. In the South, the heartland of imported fire ants, a microscope or fancy identification guides and taxonomic keys are not needed. All one needs is a good tennis shoe; that is, a tennis shoe on a good foot. I call this the “Nike” test. Simply walk up to the mound in question, give a good swift kick with the heel of the shoe to knock off the top soil of the mound, and quickly step back a few steps. If the top of mound turns black within 10 seconds with roiling ants, these ants are fire ants. At this point, take a few more steps back. The test is not without its risks. If not efficiently executed, a few ants might remain on the shoe, and these ants will inevitably crawl up the ankle looking for somewhere to sting. Stomping and fast brushing will usually solve this problem.

  People west of the Pecos River in Texas through New Mexico, Arizona, and California often think they have no fire ants. To dispel this myth, try the backyard barbecue test. It’s simple. After a warm, midsummer afternoon barbecue, when you’ve finished enjoying the chicken, toss a bone or two into the yard. To be really fancy, cover the bones with a rock or a scrap of wood. Then, early the next morning, as the sun is glowing in the east, inspect the bones. They will likely be teeming with little light-colored ants. In many cases, these little ants are native fire ants. They are similar to the imported fire ants, only less numerous and less obvious because the hot, dry climates in western areas keep the ants underground during the day where they are not noticeable. They are less numerous because, as native ants, their populations are more in balance with other species of ants, unlike the runaway population explosion in the South, where their imported brethren have taken over and displaced most of the native ants. Although less common than the imported fire ants, native fire ants in the West are not meek, mild characters. They are every bit as feisty and ready to sting as imported fire ants, as anyone who has used fingers to remove the morning chicken bone from the yard can testify.

  Are fire ants dangerous? Yes and no. No, in that most of us suffer no ill effects of fire ant stings, save the damage to our egos and the rude disruption of our peace and tranquility. The next day, other than some white, pimple-like pustules caused by imported fire ant stings, we are none the worse. A classic illustration of the usual lack of long-term damage from fire ant stings is the saga of an inebriated fellow in Houston, Texas. Here is his experience as described by the treating doctors:

  A 49-year-old alcoholic was brought to the hospital at 2 a.m. on a Sunday morning. After drinking all day and all night on Saturday, he attempted to go to a friend’s house to sleep. Arriving at the ditch in front of his friend’s home, he was overcome by drowsiness, and in the dark selected a fire ant mound as his pillow. … Approximately 5,000 of these [sting] lesions were scattered over his face, trunk and extremities. His vital signs were normal, as were the results of the remainder of the physical examination except for the strong odor of alcohol on his breath. The following morning, the patient had his “usual hangover” but otherwise felt fine.4

  In fairness, there is also a yes answer to the question, Are fire ants dangerous? The yes refers to unlucky people whose encounters with fire ant stings sadly result in allergy, not happy endings. The tiny percentage of people who are allergic to stings suffer anything from systemic skin reactions to difficulty breathing, a drop in blood pressure that causes fainting or loss of consciousness, and trips to hospitals. Curiously, the rate of allergy to fire ant stings is actually much lower than allergy to honey bee or wasp stings. Allergy to bee and wasp stings is around 1 percent to 2 percent of the population. In contrast, less than 1 percent of the population is allergic to fire ant stings, especially surprising given that about half the resident population is stung yearly in fire ant–infested areas,5 and only 10 percent or fewer of residents in bee and wasp areas are stung yearly. The reason for the lower rate of allergy to fire ants is unclear but likely related to the much smaller amount of venom protein injected with fire ant stings than with bee or wasp stings. Nevertheless, a handful of people actually die each year from allergic reactions to fire ant stings; fortunately, this is not the norm, as most of us get by with a few expletives and not much more.

  The story of fire ant venom and its chemistry rivals any good mystery thriller, complete with murder, intrigue, and detective work. Fire ant venom consists largely of piperidine alkaloids, compounds related to coniine, the main toxic component of the deadly poison hemlock. Socrates was forced to drink hemlock in 399 BCE following his conviction for impiety, essentially the excuse levied against him for being a rabble-rouser who challenged the ideas of the powerful in Greek Athenian society. Coniine is a water-soluble alkaloid; hence, it is easily brewed into a bad-tasting tea. In contrast, fire ant piperidines are insoluble in water and lack any taste, rendering them poor candidates for making a tea for murder. Their lack of water solubility also means we cannot determine how poisonous fire ant piperidines are to humans because they do not flow through the blood or lymphatic streams from sting site to the heart, lungs, or other vital organs. Instead, these alkaloids stay in the skin, poisoning the local area and causing the delayed pustule formation so characteristic of imported fire ant stings. Equally mysterious is why only imported fire ant venom causes skin pustules. Native fire ant stings don’t cause pustules; thereby, they provide a convenient, if not pleasant, way to differentiate between native and imported fire ants in the United States. Could the difference in pustule formation be related to the fact that the alkaloids of native fire ants are smaller than those of the imported fire ants and that these smaller alkaloids are more water soluble and can be carried away from the sting site? Or could native fire ant alkaloids simply be less locally toxic?

  Good sleuthing was necessary to understand the chemical nature of fire ant venom. For years, the odd nature of fire ant venom was known. Unlike most ant, wasp, or bee venoms, which are a blend of water-soluble proteins and peptides (small proteins), fire ant venoms form venom droplets that float in water and lack meaningful amounts of proteins. The venom chemistry proved elusive, first with misidentifications in the mid-1960s, followed by a high-profile report that the identifications were, in fact, wrong.6 The story was back at its start with venom being “an amine.”

  In the early 1970s, Murray Blum took up the challenge and assembled an able team to tackle the fire ant venom problem. Murray, well known for his collection of tobacco pipes that he could rarely keep lit and for his mean game of squash, was located in the fire ant heartland of Georgia, where he was suited for the challenge. In an extensive series of detailed chemical papers, he and the group discovered that “solenamine,” as the active components were called, consisted of an assortment of 2-methyl-6-alkylpiperidines with the alkyl groups ranging from 11 to 15 carbons. The coniine Socrates was forced to drink differs only in having a propyl (3-carbon) group at the piperidine 2 position in place of the 1-carbon methyl for fire ant venom, lacking the 6 position side chain entirely. The fire ant story gets even stranger. The more primitive native fire ants have mainly piperidines with 11-carbon side chains, whereas the two imported species have mainly 13- and 15-carbon side chains.7,8 Given that the main venom difference between the native and imported fire ants boils down to 11- versus 13- or 15-carbon side chain length, we might conclude that the skin pustules are probably caused by the longer chain lengths in the imported species than in the natives. Oddly, in other studies, it turns out that the 11-carbon piperidines are more toxic to fungi or a variety of bacteria than the longer side-chained components. Given that the venom appears to serve an important role in fire ant nest hygiene by controlling fungal and bacterial pathogens, why, then, would the imported fire ants evolve less effective, and more metabolically costly to produce, venom components? Could it be that increased defensive value against big predators, like humans, is the reason? We don’t know. We have many more rich mysteries about the fire ant to solve, as the fire ant does not yield its answers easily.

  This brings us to the sting of fire ants. Most
of us in the United States assume the worst is here, and often are dreadfully afraid of the stinging fire ants we already have. Never fear, others even worse might be lurking in South America, awaiting us to transport them here. According to reports from distinguished myrmecologists (people who study ants), possibly more painful candidates might include S. virulens and S. interrupta. Stay posted. But really, the stings of fire ants are not that bad. On the pain scale, a fire ant sting musters a pain level of only 1, pale in comparison to even the common honey bee. The fire ant sting is sharp and immediately sends a burning sensation to the area. The pain, however, lasts only a couple of minutes before receding to the state of “oh, yeah, I can feel it, but it’s nothing to get excited about.”

  7

  YELLOWJACKETS AND WASPS

  [Yellowjackets and baldfaced hornets] terrorize housewives,

  ruin picnics, and build large aerial nests that challenge fleet-footed

  stone-throwing boys the world over. —Howard E. Evans and

  Mary Jane West-Eberhard, The Wasps, 1970

  THE YELLOWJACKET. Mental images explode of something bright and flashy, something brash and perhaps rash, something to be watched and considered. Indeed, these images apply perfectly to yellowjacket wasps. They are bright, flashy, and require watching because they can sting. Delivering a painful sting to the oblivious or to someone foolish enough to grab one or to meddle with its nest is a yellowjacket’s special talent. Their bright yellow and black coats, indicate that yellowjackets are true masters in communicating their defensive potential or, if needed, their actual abilities to any person or other large visually attuned creature. If the potential assailant has dim vision, yellowjackets apply another warning trick. They buzz loudly with a fierce, readily audible high pitch to a wide range of audiences. This shrill buzz is different from the normal buzz of flight of a yellowjacket, bee, or fly. It is as distinctive, general, and easily recognizable as the rattling sound of an alarmed rattlesnake. The role of the yellowjacket’s buzzing and the snake’s rattle is the same: to warn the listener to stay away or suffer severe consequences. When captured, common flies attempt to mimic the same high-pitched warning buzz of a wasp or bee, only they’re bluffing. Imitating a dangerous animal by converging the sound, color, odor, or behavior of another animal is called mimicry. If the mimicry is fake, that is, the animal poses no actual threat, as in the case of the fly, it is called Batesian mimicry, named for the famous nineteenth-century naturalist Henry Bates, who first described the phenomenon. If the mimicry is honest and the animal actually poses a threat, as among the several different species of yellowjackets that look and sound similar, it is called Müllerian mimicry, after the German naturalist Fritz Müller, who first described in detail this form of mimicry.1

  When given the chance, all young children are naturalists. Like other children, I was a young naturalist, who, in my case, happened to be enraptured by yellowjackets, and that biggest of yellowjackets, the baldfaced hornet. Their active, seemingly carefree style of flitting about in the warm sunlight was appealing. Their bold colors added an air of excitement. They challenged me to find where they were going and where they lived. Once I located their nest more opportunities were revealed. How close could I get without them noticing? Could I count how many came in and out in a minute? What will they do when presented with a challenge? Once I watched with youthful fascination as my father, a venerated Wisconsin forester brimming with practical natural history wisdom, decided to see whether he could eliminate a yellowjacket colony living beneath the masonry stone steps leading to our porch. He didn’t want to kill them by pouring gasoline into their entrance at night, the unapproved, though traditional, way of dealing with yellowjacket colonies, for that would leave a smelly and potentially unsightly mess. Lighting the gasoline, the exciting flaming climax of traditional yellowjacket eradication, was too hazardous and illegal for his style and personality. He also didn’t want to poison our front yard with typically foul-smelling, and likely unsuccessful, chemical sprays. The chosen solution was to fill the entrance with mortar to trap the wasps inside. We went out with a red cellophane-covered flashlight (yellowjackets cannot see red) and filled the entrance hole. The next morning yellowjacket colony life was as normal. They had simply dug through the moist mortar at night and continued life as usual. The next night we stuffed some steel wool down the entrance to block it and filled in mortar again. The yellowjackets buzzed softly from within during the process, but they could not attack us. Fooled again. This time the yellowjackets dug a side tunnel through the earth beneath the walkway and exited a short distance away. I learned from this experience that these insects, like people, were good at solving problems and adapting to challenges that nature might bring to them.

  My father ensured we did not get stung during these adventures. He knew the painful sting of yellowjackets, and, as a good parent, he wanted to protect me from getting stung. I viewed the operation as a good, clean learning experience but certainly not high adventure. For this, I would tag along with neighborhood boys as we played in the streams, fields, and woods looking for snakes, frogs, toads, worms, or anything else that caught our attention. We were game hunters in the tradition of our long-ago ancestors in Africa, only we hunted small game, and we didn’t eat it like our ancestors would have. On a pleasant summer day, one of the older boys came upon the perfect small game, a baldfaced hornet nest. Soon we were throwing rocks in the direction of the nest. And, yes, I was stung. Screaming and yelling were all part of the adventure—as we were all screaming—but no crying was allowed. I licked my wounds in silence.

  The yellowjacket episodes instilled several lessons. First, nature is a two-way street. If you act toward another creature, it will respond to your action. Second, we as humans cannot always dominate and predict the consequences of our interactions in the natural world. Finally, nature, insects, and stinging insects, in particular, are thrilling. Children are simply untrained scientists, and scientists are simply trained adult children. Around the age of 12 or 13, we move into the ranks of young adults and are expected to leave childhood behind, except in memories. In junior high school, we learn rigorous academics and trades. My interests shifted first toward math, especially geometry, then to physics, and finally to chemistry. Insects and biology were left behind, but not forgotten, by the boy within me.

  Years later my chemistry and entomology training took me to Costa Rica where I studied the ecology, genetics, and defensive behavior of killer bees. In genetic terms, killer bees are simply biological wild-type honey bees that had not yet been inbred, genetically modified, or domesticated. The brilliant, talented geneticist Warwick Kerr had brought them over from the Pretoria region of South Africa by request of the Brazilian government. They escaped captivity, were better adapted to the warm climate of Brazil than the domestic bees previously introduced, and in their northward range extension had reached Costa Rica. They still retained their full range of natural defensiveness against human and other mammalian predators.

  On a break from bee work, I and Hayward Spangler, an expert in insect sounds and acoustics, decided to visit Frank Parker, who, at the time, was investigating the ecology of screwworm flies. Frank is a tall, impressive, distinctive man who was locally referred to as “malo Gringo grande” for his friendly manner combined with an unstoppable energy as a human vacuum cleaner sucking up any insects and spiders he could find in the field. His sense of humor extended to taking visitors to the field to help capture screwworm flies attracted to a festering three-day-old mash of rotting pig liver. He got great delight in watching the expressions on the faces of hardened entomologists when he slammed his white insect net onto the pile of rotting liver to capture a fly.

  The day we visited Frank, he was in a forest meadow at mid-level elevation along the western slope of a mountain range in Guanacaste Province, Costa Rica. Hayward and I left Frank to his flies and went exploring for any interesting ants or wasps that might sting or make sound. Success was close at hand, about a
hundred meters up from Frank’s camp. In a small, thorny, nearly impossibly dense bush was a large nest of Polybia simillima, a tropical epiponine wasp, independently noted by the early twentieth-century naturalists Philip Rau and, later, O. W. Richards for its especially painful stings and its ability to leave its stinger in one’s flesh. Opportunity knocks and then flees. I was not about to let this opportunity flee. Frank and Hayward declined, preferring to stay with the flies, while I donned my bee suit, complete with protective veil, to bag the wasp nest for dissection, venom collection, and analysis. In all my tropical experiences, I had never encountered this uncommon species before and was not about to miss the opportunity. I had learned previously that any black stinging insect is telling me something and needs to be approached with utmost care. These menacing wasps are black, buzz fiercely, attack with speed and agility, and leave their stinger in your skin, all properties I had anticipated. With clippers to remove the spiny branches and a bag in hand, I expected the operation to be routine, and I would have my wasps. Wrong. The lessons from childhood experiences with yellowjackets returned. These wasps were able to find solutions to the problem at hand—an entomologist threatening their nest. Their solution was simple: crawl through the mesh of the bee veil and sting. Four to five stings later I attempted to set the 100-meter-dash record in a bee suit in the downward direction toward base camp. There I was greeted with apprehension by Frank, who said, “Don’t bring those wasps down here.” Hayward, being more fatherly and understanding, helped me put on an army issue, green mosquito head veil under my bee veil. That should solve the problem. Wrong again. Earlier lesson learned from yellowjackets reinforced. This time the beautiful black wasps flew through the veil and summarily crawled under the elastic of the mosquito netting. Half a dozen stings later and it was déjà vu, a screaming 100-meter dash in full garb back to base camp. This time a few wasps accompanied me. As a wasp buzzed him, Frank’s demeanor changed from apprehension to annoyance: “Don’t come back here again. Stay away with your wasps. I don’t want to get stung.” Undaunted, though in pain—these wasps hurt a lot more than yellowjackets or honey bees—and with Hayward’s help, we tried again. This time Hayward liberally applied silver duct tape around the entire juncture between the mosquito veil and my sweatshirt under the suit and around the juncture where my pants covered my boots and my sleeves covered my surgeon’s nitrile gloves. Ignoring Frank’s mutterings, off up the hill I went. This time sweet success. The prize was mine, and a major gap in my data on venoms of stinging insects was filled.