The Sting of the Wild

by Justin O. Schmidt

  Two elements of wasp behavior color prey-stinging observations. Capturing prey is an energetic endeavor that requires oxygen. Yellowjackets, like most insects, breathe via tracheal tubes to their tissues with air moved by abdominal pumping much like an accordion. Because the sting is sheathed inside the pointed tip of the abdomen and is thin and black, it is impossible to see the sting when it is ephemerally exposed during stinging. Our expectations lead us to conclude that abdominal pumping drives home the sting. Another befuddling feature of prey-capture behavior is purely mechanical. We naturally carry infants or other heavy objects by holding them against our side and supporting them on our hips. Our hip serves as an extra arm. Yellowjackets have no hips, but, like us, sometimes need an extra arm to control and manipulate struggling prey. The tip of the abdomen is that handy, mobile extra arm. This use of the abdomen fits expectations perfectly for stinging.

  A final factor in our prey-stinging tale is the confusion of defense with predation. When a predator attacks, a yellowjacket or other stinging insect will attempt to sting in personal defense. Such defense was witnessed in the case of wasps struggling with attacking spiders or dragonflies. If the wasp wins the struggle, its behavior then changes to predatory and the former predator is butchered and carried off to the nest. Carl Duncan expressed prey stinging succinctly: “These statements the writer believes to be simply errors based on preconceptions rather than precise observations.”8

  Ironically, stings must sometimes fail if they are to become effective defenses. If yellowjackets had no predators, their venomous stings would never have evolved in the first place. Natural selection quickly weeds out unnecessary energy-requiring body parts. If the sting is not needed, it would have gone the way of blind cave fish eyes; the ancestors of blind cave fish had perfectly functional eyes. Alternatively, if the sting were only marginally effective against major predators and competitors, it might have gone the way of forest thatching ants, whose sting modified into a nozzle that sprays formic acid. The key to the evolution of the sting was that it sometimes worked. Those queens and their workers that possessed stings that defeated more predators than other queens and their workers with less effective stings would be at a selective advantage for passing their genes, including their particular version of the sting, to the next generation. Predator filtering of the gene pool for stings is the driving force for the evolution, improvement, and maintenance of the sting. As the yellowjacket sting became more effective against more potential predators, it opened ecological doors of opportunity. Now, rather than being defenseless tasty morsels, leading unobtrusive, restricted lives, defended yellowjackets could venture afield during daylight to visit flowers for sweets or fresh cow pats in the meadow for flies. And produce more babies.

  I have experienced firsthand one additional benefit of wasp stings (for the wasp, that is). Like the forest thatching ants, some wasps also spray venom, not formic acid but proteinaceous venom with lytic and painful components. I first suspected this behavior as I was antagonizing a colony of eastern yellowjackets. I succeeded in arousing hundreds of workers to fly around my bee veil, attempting to enter and sting. Suddenly, the air became redolent with a sweet-smelling perfume. The odor was rather pleasant and flowery overall, even if the situation was less than pleasant. Where did this odor come from, and what was its function? The answer to the second question was abundantly clear. As soon as the odor appeared, the ferocity of the yellowjacket attack increased dramatically. The odor was a pheromone signaling alarm and recruiting more sisters to battle. Its source? I suspected the venom. Back in the lab when a fresh venom sac was crushed, sure enough, the odor arose. No other part of a yellowjacket produced the odor. Also, while the odor was present in the field, the air around my face became irritating and unpleasant. The workers were spraying microdroplets of venom into the air. These droplets were release devices for the pheromone.

  Yellowjacket venom was not that bad when it was sprayed into the air. At least it didn’t affect me directly. That was not the case with another species of social wasp in the tropics. Parachartergus fraternus, a lovely, delicate shiny black wasp with clearish white wing tips, makes beautiful artistic nests of undulating delicate waves that form into a thin, gray paper that covers the combs. In Costa Rica, nests are often built in small trees several meters aboveground. The mere fact that these wasps are black signals beware.

  One day while driving along the steep road to Monteverde, Costa Rica, with my assistant, we saw a particularly nice nest on a small tree on the left side of the road. The nest was located about 3 meters up in a 15-cm-diameter tree that was leaning at an angle about 20 degrees over the abyss of the valley below. The operation seemed a snap. Simply don my bee suit, shinny up the tree with a bag in hand, carefully slip the bag around the nest, break off the branch holding the nest, and, presto, I would have the nest. The wasps seemed to have other ideas. As soon as I started climbing, the vibrations alerted them, and they watched but did not fly or attack, even when I was right next to them. During this time, I was holding my breath to prevent a massive attack. (That part of the operation worked.) All was going as planned until the bag hit a snag and failed to surround the entire nest. This effrontery was too much. The wasps exploded off the nest at me. They couldn’t get through the veil, but they had another trick up their sleeves. They sprayed streams of venom through the mesh of the veil directly at my eyes. As soon as the first bit of venom hit my eyes, I closed them tight, preventing more potential damage and pain. Meanwhile, I’m up 3 meters over a cliff with a nest only partially in the bag, and I can’t see. Not wanting to lose this opportunity, I somehow got the nest entirely in the bag, broke off the attaching branches, and slid blind down the tree, prize in hand. My helper led me to the car and drove us off. The pain and eye watering continued for some minutes; fortunately, the venom is water soluble and the tears eventually washed it away.

  WE HUMANS DO NOT CONSIDER yellowjackets among our best friends. In the words of Howard Evans and Mary Jane West-Eberhard, “Wasps are not the most popular of animals, for it is hard for us to reconcile ourselves to creatures so well equipped to defend themselves.”26 The theme is continued by Harry Davis: “Almost without exception, people did not want the wasps on their property, and their primary concern was being stung.”27 The earliest written record of wasps relates to Egyptian King Menes, the long-ruling, powerful first Egyptian pharaoh. Historical fancy records his death as caused by a wasp sting. As the story goes, King Menes was stung and died about 2641 BCE, while adventuring on a warship near Britain. As delightful and imaginative as wasp lovers and allergists would like this story to be, the king was not killed by a wasp. Most likely he was killed by a hippopotamus while navigating the waters of the Nile River. The inner message of this story is unclear: Is it simply to show how strongly wasps affect our emotions and fears? Or does it imply that we are more frightened of wasps than hippos?

  Aristotle, some 2,300 years ago, was the first scientist to write about yellowjackets and hornets. He described their stings as stronger than the stings of honey bees. Aristotle provided many accurate descriptions of their lives. He noted that drones were stingless and debated whether their leaders (queens) had stings. (He concluded that they likely had stings but did not put them to use.) An era of superstition and romantic ignorance followed Aristotle. Romans believed that yellowjackets were generated from dead horses, that hornets were special, emanating from dead warhorses, and that honey bees emerged from dead bulls. These beliefs continued into sixteenth-century Europe. Only in 1719 were the beginnings of modern scientific understanding of wasps established by the observant French naturalist M. de Reaumur.28

  Do these stories and history tell us that yellowjackets and hornets are winners in the human-stinging insect game of life? Several lines of evidence suggest the answer is yes. In the United States, only about 50 people die per year from the combined stings of all stinging insects (wasps of various types, honey bees, and fire ants).29 At the same time, 10,000 times as man
y people die from smoking; and diabetes kills a thousand times as many. Do we tell stories at cocktail parties of our narrow escape from a smoke-filled environment or of overcoming the risk of that enticing sugary, fatty doughnut at the coffee break? But we relish telling stories about surviving an encounter with a stinging insect. The message seems clear. Stinging insects win the emotional fear game. We are afraid, if not outright petrified, of stinging insects; yet, we fear not smoking, diabetes, and other many-times-more-dangerous and preventable aspects of life. Until the advent of modern technology and ways of killing yellowjackets, the wasps won, and we largely left them alone to go their own way, doing exactly what they wanted.

  The evolutionary mind game between humans and hornets has been fascinating. We do not simply fear stinging insects; we entertain ourselves with our fear of them. We relish and embellish the fearfulness of stinging insects to make an even better story. One sunny July afternoon in 1999 an editor of Cosmopolitan magazine called and left a message that she wished to interview me. Not fancying myself as an expert on women’s social culture or fashion, I asked my student Andrea for background information about the magazine. You should have seen the horror on her face: “Cosmo wants to interview you?” With trepidation, I approached the interview. To my relief, Cosmopolitan sought my knowledge about stinging insects. Why was Cosmopolitan interested in yellowjackets? Turned out they were worried about the safety of their young readers as they frolicked in the woods during fine autumn afternoons, and the editors wished to write a reassuring story. Score one point for the yellowjackets.

  More recently, our old friend Vespa mandarinia (the mandarin hornet), the largest stinging insect in the world, has been the subject of news stories in China. Headlines read: “Killer Hornets Rampage through China,” “Giant Killer Hornets Kill 42 People in China and Injure More Than 1600 Others,” “Giant Asian Hornets Are Killing People in China, Breeding in Large Numbers.” One article pictured four hornets that spanned the entire width of a person’s hand. My first thought was, “Wow, those sure are huge hornets,” which presumably was the intended impression. My internal BS app kicked in. Something was awry. I just happened to have in my insect cabinet, three steps from my desk, two queens, the largest individuals of mandarin hornets, which, in turn, are the largest of all hornets. I placed these in my left hand. They only spanned slightly over half the width of my hand. My hands are average to smallish for adults. How could that be? I caught my queens in Yun Xi (pronounced “Ywen shee”) bamboo forest near Hangzhou, China, where they appeared to be hummingbirds slowly cruising the forest floor. These queens were the real thing. The article didn’t specify the age of the person, nor show more than the hand. I put the hornet in my 11-year-old son’s hand and perfect match! Apparently, as if wasps and hornets are not already big enough, we have to make them even bigger. Score another point for yellowjackets and hornets.

  The power of yellowjackets to influence human emotion extends even to our legal system. Yellowjackets fall under the English tort law section covering “knowingly and willfully harbouring a dangerous vicious animal.” Flies, grasshoppers, and praying mantises don’t fall into that category, but bees and wasps do. I was brought in as an expert witness in a case in which a lady purchased a strawberry cake roll from a large national retail chain store in Billings, Montana. She got the munchies near midnight one evening and ate a slice of this cake roll. No problem. However, the next morning she ate a piece of cake and was stung by a “bee” in the cake roll, had an allergic reaction, and was treated at the hospital emergency department. Was this product liability of the cake manufacturer or of the retail store? I testified that the German yellowjacket (not a bee) could not have been alive at the time of the perceived sting, as the cake was manufactured and sealed in plastic a few days earlier, 1,600 miles east, and that the yellowjacket was thoroughly embedded in pink frosting, evidence it was caught in the cake during manufacture. A worker wasp could survive that treatment, at most, for a few hours. And, no, the wasp couldn’t have flown into the cake at the store because the cake was sealed at the time of purchase. Further examination revealed the sting of the gooey and somewhat crispy yellowjacket was completely withdrawn into its abdomen. The sting tip was intact, not bent, and not broken off. Case closed. The wasp was innocent, and the lawyers and the wasp won. Score another point for the yellowjackets in the psychological battle with us.

  As with fire ants, humanity has not lost the battle against yellowjackets willingly. Dislike and economic damage are a prescription for war. Angry fruit growers dealt with damaged crops, park and resort operators closed or limited activities, loggers shut down operations, firefighters were thwarted as they fought forest fires, and beekeepers’ beehives were under attack all because of yellowjackets.30 Action was needed to combat the yellowjackets. Lead arsenate to the rescue. But it didn’t kill colonies. Next, the miracle insecticides—DDT and chlordane—were added to horsemeat baits. Intense baiting lowered the worker populations in local areas,31 but insecticides are environmentally harmful. Mirex, the wonder insecticide developed for fire ants, also worked in baits but was environmentally unacceptable.

  An intense effort was devoted to finding the perfect yellowjacket bait. Initially, tuna fish baits and other fish flavors were favored, especially Puss’n Boots fish-flavored cat food.32,33 The reign of cat food did not go unchallenged. John MacDonald, research professor at Purdue University, and colleagues visited a local zoo and observed that yellowjackets actively scavenged from Nebraska Brands feline food fed to the zoo’s big cats, not domestic felines; nevertheless, it was highly attractive to yellowjackets. This horsemeat-based diet was vastly superior in attracting these Lilliputian carnivores than Puss’n Boots or four other tested cat foods.34 Two years later boiled ham was found more attractive than the Nebraska Brands horsemeat product.35 Not to be outdone, E. B. Spurr in 1995 tested nine types of fish and seven meat types for attractiveness to yellowjackets in New Zealand.36 Venison was most preferred followed by hare and horse; beef was least preferred (all fish were between beef and horse). Should picnickers avoid venison or rabbit sandwiches in preference to beef?

  In New Zealand, a country plagued by explosive populations of invasive German yellowjackets, one proposal was to pay a bounty on each yellowjacket queen captured to prevent the establishment of colonies. The hunt was enormously successful with kids (and adults) enthusiastically delivering 118,000 queens over three months. Everybody had fun in this adventure until the next season when the yellowjacket population appeared unaffected. A similar bounty program was conducted in winter in Cyprus, again with enthusiasm (huge amounts of money was paid), only to be followed the next year by one of the worst wasp seasons in years.15 Yellowjackets were the winners again, but at least these eradication programs were environmentally benign.

  Generals in the yellowjacket wars concluded that a new approach was needed. The best baits had twin disadvantages: they contained toxic materials and rapidly spoiled or became dry and unpalatable. Instead of poisoning colonies with baits that yellowjackets take back to the nest, why not deal directly with the foragers? After all, the foragers were the problem, not the colonies. Why not trap them directly and take them immediately out of the system? Thus, nontoxic chemical attractants in one-way traps became the preferred means of yellowjacket control. Harry Davis, a man of concise writing and practical approaches, tackled the problem head on. Over several years, he and his group tested innumerable compounds for attractiveness to yellowjackets, culminating with a massive screening of 293 different attractants.37 From these screenings, first came the attractant 2,4-hexadienyl butyrate, then heptyl butyrate, and finally octyl butyrate. Over four days, these attractants lured 200,000 foraging yellowjackets to their doom in traps—enough to fill a wheelbarrow—and successfully saved the crop on an 8-hectare peach orchard. Thus, we could win small battles against yellowjackets. Perhaps that is enough.

  One way to win these tiny battles with yellowjackets is to get up close and personal. If a yello
wjacket stings us, usually because we are too close to a colony, we can get revenge. Locate the nest entrance somewhere nearby, typically in our yard. Over the years, many solutions have been proposed, including a variety of toxic insecticides that are puffed, sprayed, or flooded down the entrance tunnel at night, followed by sealing the entrance (be advised to use a red light, wear protection, and keep from breathing on or near the nest). Several more benign materials have also been proposed for use in place of toxic insecticides. Curiously, perhaps for legal reasons, a most effective method is almost never mentioned in American literature. Every rural or farm child knows that gasoline (or kerosene) kills insects instantly. Gasoline is not registered for control of yellowjackets or any other insect, so professionals cannot recommend or even acknowledge its use. I am not recommending it either, just providing some history of this fraught-with-danger folk remedy.

  I experienced firsthand yellowjacket control with gasoline while making fire trails for a logging company in the Pacific Northwest. We cut and removed vegetation and scraped to bare earth a trail 2 meters wide around an area to be logged. That way, if a spark from a piece of machinery ignited a fire, we had a barrier and could stop the fire at the fire trail. The team consisted of four people: two buckers with chain saws to cut through downed logs and saplings in the way and two people to wield hoe dads (oversized mattocks) to scrape to the earth. All too frequently, the buckers stirred up a yellowjacket nest. Instant command: “Grab the gasoline can.” Someone would grab the goosenecked gas can, carried along to refill the chain saws, stick the spout down the nest entrance, and pour in a liberal amount of gasoline. Problem solved. A few expletives later and we were back on the job. Fire and gasoline do not mix; they explode. The buckers never lit the gasoline. After all, we were preventing, not making fires. But burning is an unfortunate human national pastime. We burn fields, roadside vegetation, and yard waste. Fire is fascinating. And by human nature burning yellowjackets seems especially exciting and satisfying. The average person all too often lights the gasoline after pouring it down the yellowjacket nest. Never mind that this is dangerous and ineffective because all it accomplishes is making fire aboveground where there are no yellowjackets and fire more quickly evaporates the gasoline inside the nest that is actually doing the killing. Word to the wise: don’t light it. Doing so might rip disaster from the jaws of victory in a battle with yellowjackets. Another, even sillier idea was proposed in 1770 for colony control. Add “wetted” gunpowder, light it, and the fumes will kill the yellowjackets.38 And we think modern-day people live dangerously.