The pain caused by the sting is nothing serious. It’s pure, clean, and tidy, like “a tiny spark has singed a single hair on your arm.” The pain is not likely to get you serious sympathy; that is, unless one is a small child, in which case no excuse is really needed for hugs and sympathy. The pain goes away momentarily and leaves little evidence of its occurrence. The sting rates a classic 1 on the sting scale, thereby providing a convenient reference for comparing other past and future stings. It certainly does not in any fashion compare with the pain of a honey bee sting, rated 2 on the sting scale.
FIRE ANT. NOW THERE’S A NASTY ANIMAL. Unlike sweat bees that mean no malice as they sweetly go about their business pollinating flowers we love and foods we enjoy, fire ants have an attitude. Humans also have an attitude toward fire ants as expertly expressed by Walter Tschinkel: “Most people hate fire ants without reservation, without reflection. Perhaps that is what the fire ant has to offer us—something we can all agree to hate, something about whose reprehensibility no argument can be made.”1 For their part, fire ants’ first response to contact with human flesh is to sting. Fire ants have not learned how to make friends and influence people. Who are these fire ants? What do they do? Where did they come from? Why are they so nasty? How do I get rid of them?
Fire ants are small polymorphic (many different-sized individuals in one colony) ants belonging to the largest and most successful subfamily of ants, the Myrmicinae. They are all in the genus Solenopsis, a 185 species–strong group that has frustrated some of the greatest ant scientists, including Carlo Emery, William Creighton, William Buren, and Roy Snelling. The frustration arises in large part because the smaller worker ants, called minors, are amazingly similar among species to most anyone who has not devoted much of their life to ant taxonomy—and even to some who have. The comment regarding ants in general made by William Morton Wheeler in 1910 that “the species of ants often differ from one another by characteristic too subtle and intangible to be readily put into words”2 applies especially to fire ants. For easiest identification, major workers, the largest “big headed” individuals, are required, and they constitute a minority of the overall population. Imagine the fun of searching for the largest ants while picking through a swarming mass of outwardly oozing stinging ants and the problem becomes clear. The other problem in assigning names to fire ants is that over the years too many experts have further confused the already-muddled situation by making unnecessary changes, causing an exasperated Roy Snelling to comment about one author: “The best method of dealing with this volume is to disregard entirely the statements of the author.”3
Fire ants are loosely grouped into the fire ants proper and the “thief ants,” the latter category with more species by far. Thief ants make their living by stealing from other ants. These tiny ants build their nests in conjunction with other ants and proceed to dig tiny tunnels that join into the chambers of the other ants. From these tunnels, worker thief ants raid and steal brood (immature ants: eggs, larvae, and pupae), which they take back to their own colony to consume. They succeed partly because their tunnels are too small for passage by the host ants. Thief ants cannot sting humans and are invisible to all but a tiny portion of people who actually care about them.
Ants in the other category, true fire ants, are larger and of more concern to humanity than thief ants. These ants all sting, all are nasty, and all originated in warmer areas of North America and South America. Their behaviors, like their general appearances, are similar. If you’ve met one fire ant, you’ve met them all. All fire ants build large colonies of thousands to hundreds of thousands of ants. They are all polymorphic, with a range of small to large ants, and eat almost anything that comes their way and provides calories—live prey, dead animals, seeds, nectar, honeydew, or other plant material. Fire ants aggressively defend their territories and attack intruders. They all sting, and those stings hurt. Fire ants probably all form into balls that float on the water’s surface when floods come. Six species can be found in North America. Three, the southern fire ant (Solenopsis xyloni), the pleasantly named golden fire ant (S. aurea), and S. amblychila are long-established natives. Another species, the tropical fire ant (S. geminata), might be native to the United States or might have migrated naturally or with assistance from humans many centuries ago. The final two fire ant species are the “imported” fire ants (a peculiar name that implies they were introduced by desire), S. invicta and S. richteri. These two were both transported from South America to Alabama in the first half of the twentieth century.
My first encounters with fire ants came in the 1970s when I was a graduate student at the University of Georgia. I had vaguely heard horror stories in the news of these invading ants from South America who were abusing southern hospitality. Otherwise, I knew little about them. What an opportunity to see them up close. My first reaction was disbelief. These ants are tiny, not at all like the big, self-respecting ants I was familiar with. From their reputation, I expected something enormous. The second impression came quickly as I brushed some loose soil from an ant mound to look inside. The ant reaction was swift and decisive. They immediately crawled onto my hands and up my arms, many stinging, as the horde moved ever farther upward. These ants are nasty. They don’t just bite, a minor pinch delivered by most of the ants I had known, they bite and sting. The name fire ant accurately describes their stings. When dozens sting at once, a habit for which they are famous, that unlucky part of the anatomy feels on fire. The bite is inconsequential. I am not sure I have ever felt the bite. The sting overwhelms the bite sensation, which is lost in the surrounding sea of pain.
Although fire ant stings are unpleasant, fire ants are fascinating. The fire ant life cycle starts out as typical for most ants, with winged virgin males and females (queens). They embark on mating flights during warm, pleasant spring and summer days in which thousands engage in the mating ritual, actually a mating frenzy, with airborne pairs grappling, falling to the ground, and mating. This is furious sex in the fast lane, with only one chance to get it right. Males and females mate for 10 seconds, once in their lifetime. Males need to act quickly. They die or are killed and dragged off by other ants within hours of leaving the nest. The mated females break off their wings, often leaving a chaff of discarded wings blowing in the breeze, and scurry about looking for a suitable nest site. Time is precious. Ant queens are universal desserts for most small or large predators. Once a nest site is found, the queen, sometimes joined by other queens, digs a short tunnel in the soil, seals the tunnel entrance with soil, and makes a cell in the bottom. Here she raises a few tiny “minim” workers entirely from her body reserves of stored fat and metabolically cannibalized wing muscles. Once they reach adulthood, the minims go on raiding parties to steal brood from other queens. Along the way, many queens die or are executed, resulting in a few surviving micro colonies. The minims forage for food, rear the first normal-sized workers, feed the queen, and take over all nonreproductive colony activities. The colony is on its way.
Returning to the nitty-gritty of fire ant sex, each mated queen receives only about 7 million sperm with her one mating. She has to raise millions of workers from one 10-second mating and 7 million sperm. She must use her sperm wisely and sparingly if her colony is to thrive, live long, and reproduce. She uses only about 3.2 sperm for each successfully reared worker or virgin queen1 (and some larvae are eaten or otherwise die before adulthood). Compare this to human use of about 100 million sperm per offspring, assuming fertilization is successful, and the efficiency of the fire ant queen becomes obvious. The queen’s small colony grows from a handful of workers to a thousand or so in a year, to tens of thousands by year 2, to nearly 100,000 by year 3, and to 150,000 by year 4. Final colony maturity occurs around year 5 and stabilizes thereafter at around 200,000 to 300,000. The colony dies at a ripe old age of 5.5 to 8 years because the queen runs out of sperm and cannot produce more workers.1 For a queen, it pays to be frugal!
An individual ant, whether it’s a work
er, a queen, or a male, starts as a tiny egg laid by the queen. This egg, like the rest of the 2 million to 3 million eggs the queen will lay over her lifetime, hatches into a tiny larva, a translucent, whitish blob that lacks legs and the ability to defecate. However, it can, and does, readily eat the food provided by attending workers, growing over a thousand-fold in weight as a result. Periodically, during this growth, the larva molts, shedding its undersized skin in exchange for a larger skin in which to continue growing. Finally, the larva arrives at its terminal larval instar and eats its last meal. Meanwhile, it has not defecated during this whole process. Like the sweat bee it has no connection between the hindgut and rest of its digestive system. Perhaps this connection did not form earlier to prevent contamination of the nest. When the connection finally develops, the larva takes an enormous dump, called the meconium. (We can only imagine how this feels to the larva.) What happens to the meconium? Specialist workers rapidly collect it, lick the oils from it, and then deliver the oils to the queen. This adds new currency to the old saying, “What goes around, comes around.” The dried meconium is discarded. Apparently, within its oils are the precursors to juvenile hormone, a stimulant that activates egg production in the queen. The now shrunken larva molts into a pupa, the resting stage during which the adult ant is developing. The adult ant emerges from the pupa and takes up its role as part of the colony “superorganism.” Workers live several months before dying, often from the challenges and risks of foraging; meanwhile, the reproductives wait for their magical moment—the mating flight.
Like sweat bees, fire ants also have a mysterious Dufour’s gland. In sweat bees, the Dufour’s gland serves as the painter and sealer of their larval home. In fire ants, the Dufour’s gland is the chemical jack-of-all-trades and the master of chemical communication. When a fire ant forager discovers a bounty of food, she runs back to the colony dragging her abdomen. Shortly thereafter a group of recruits leaves the nest, following the trail left by the abdomen-dragging ant. The trail they follow originated from the Dufour’s gland of the successful forager. She only needs to lay a trail of 0.1 picogram per centimeter for the nestmates to follow. That is less than 1 divided by 3 followed by 14 zeros of an ounce. In addition to making a trail to follow, the Dufour’s gland activates ants to follow, something analogous to getting the donkey’s attention before it will move.
Man’s best friend may be the dog, clearly not the fire ant. In contrast, the fire ant’s best friend is man. In the words of Walter Tschinkel, the grand master of knowledge about fire ants, “If fire ants have a religion, humans must surely occupy the position of God, preparing a place for them.”1 To appreciate why we might be gods to these little creatures, let’s examine the ant’s life. Fire ants like soft soil, especially sandy soil that is easy to dig. They also like warm, sunny areas, preferably those with grass intermixed with other plants. The ideal fire ant habitat contains a variety of food resources, insects, and other small prey, along with seeds and other plant sources. The ideal habitat also has few other ants competing for space and resources. Such areas are disturbed habitats, or what ecologists call successional habitats, in which no established species strongly dominates for long. These areas are perfect for tramp species and other weedy species, including fire ants. In essence, fire ants are simply six-legged weeds. In nature, disturbed areas are relatively scarce, occurring mainly after fires, floods, powerful storms, major pest/pathogen outbreaks, or huge tree falls that dramatically alter an area. Humans raze land to plant crops, to graze cattle and other livestock, to culture grass and lawns around their dwellings and spaces, and intentionally or unintentionally, to burn areas. De facto human activity maintains these areas in a state of permanent disturbance. Human disturbances reduce or eliminate many competing native ant species, making these areas perfect for fire ants.
Fire ants share properties with many other weedy species. They grow rapidly, reproduce prolifically, quickly invade disturbed areas, and fiercely compete with other species. Humans supplement our regular activities that produce the disturbed areas ideal for fire ants by giving fire ants another special gift—insecticides. We declared war on fire ants with our insecticides. The great naturalist E. O. Wilson once described the insecticidal war on fire ants as “the Vietnam of entomology.”1
The war started on a small scale in the 1940s with government agencies dumping calcium cyanide on fire ant mounds in attempts to eliminate them. The attempts failed. Next, with no scientific background to support the operation, the wonder insecticide chlordane, a nasty, persistent, environmentally destructive chlorinated hydrocarbon, was added to the arsenal. With no meaningful success (the ants were spreading like wildfire), the chlordane club was replaced with the newer clubs of heptachlor and dieldrin, also nasty chlorinated hydrocarbons. Surely, these should solve the problem. Again, as should have been expected based on a lack of good science or understanding, the fire ant prevailed and continued relentlessly expanding its range and population. The environmental effects were so disastrous, except for the fire ant, that the program was modified and then halted. Ah, yet a better club was needed. Enter Mirex. As the reader can now expect, this program, too, failed miserably, and the ant continued thriving and enjoying the fruits of human labor. By the mid-1970s, the Mirex adventure was in its last gasps. About this time, the target of this war, the “red” imported fire ant was described as a new species by William F. Buren, a mild-mannered, soft-spoken gentleman generally given to understatements. Bill named the species S. invicta, in reference to the Latin “invincible,” apparently his way of responding to the failure of the fire ant wars.
Have we won the war with the fire ant? Not by a long shot. The score is in, and the fire ant is winning. Extensive air bombing of large areas of the South with poisonous insecticides failed to eliminate the ants. In fact, our actions helped fire ants to reduce or eliminate competing ants that, after decimation, are not able to recolonize as quickly as fire ants. Mowing lawns also failed to rid lawns of ugly mounds or the unpleasant ants; they only succeeded in splattering soil around and shortening and broadening ant mounds. We have also failed to control the spread of the fire ants to new parts of the country. Fire ants are now present in Southern California. We have had a few successful skirmishes in this war. Imported fire ants got footholds in Yuma and Phoenix, Arizona. Both introductions were eradicated, perhaps with the aid of a hot and dry climate, conditions not conducive to fire ants.
The failure of humanity’s war on the fire ant left homeowners in the South without weapons against the ants in their yards. About this time, Walter Tschinkel at Florida State University in Tallahassee formed a research group called the Fire Ant Research Team, complete with a logo featuring a menacing-looking fire ant standing over the Florida state capitol circled by the motto “Today Florida, Tomorrow Dixie.” One of the tasks of this distinguished team was to provide some relief to the beleaguered homeowner. In a viscerally satisfying way, the team did score a small victory over individual fire ant colonies. The solution was a simple, safe, nontoxic, and highly satisfying means of killing colonies, and it cost nothing, spare a penny perhaps for energy. The technique is simple: boil 3 gallons of water, select your favorite fire ant colony, and slowly pour the 3 gallons of water directly down the center of the mound. When done carefully with minimal run off, the hot water penetrates deeply into the soft mound, killing not only most of the adults and brood but also the queen. With a high success rate, this method provides temporary relief and the inherent satisfaction that a small environmentally benign victory was achieved.
The point of the digression into the fire ant wars is to illustrate how people are the fire ant’s best friend. Our everyday activities greatly helped the fire ant, and our insecticidal overexuberance ensured its success in its new home. How could this be? The fire ant, like any other colonizer or invader, must battle with any current residents for space, food, and other resources. If the resident population is large, strong, and established, the battle spoils usually fall to th
e residents. If the residents, in this case other ants, are eliminated or weakened, the invader’s job of colonizing becomes much easier. The insecticidal wars did just that. They eliminated most of the established resident ants (along with any fire ants that might have been struggling to make it). The playing field was leveled for fire ants or, should we say, prepared in their favor. With little or no competition from native ants, the reproductive fire ant queens that settled in the vacated land had excellent chances for success. This scramble is lopsided in the fire ant’s favor. The originally established ants in the habitat generally produce fewer reproductives, and their reproductive flight season is usually short. In contrast, invading fire ants, as is classical for tramp species, produce prodigious numbers of reproductives, and their reproductive flight season is long, typically covering the entire warm part of the year. These traits give the fire ants a powerful heads up over native ants in the struggle for the newly cleared areas left after the insecticidal depopulation is over. Soon the treated areas are teeming with thriving fire ant colonies. With humans as their best friends, fire ants need not worry about their enemies.
In fairness to the fire ant, we should say that it can be man’s friend, albeit perhaps not the best friend. Humans like disturbed areas, such as fields and pastures, where crops and domestic animals are grown. Within the rows of crops or pasture spaces live crop and animal pests that compete with us for the spoils of our labors. Fire ants that inhabit these fields and pastures can be useful, maybe even welcome, predators of pests, such as the sugarcane borer, a caterpillar that destroys sugarcane plants in Louisiana; boll weevils and pink bollworms that ruin Texas cotton; mosquito eggs in floodwaters of rice farms; and horn flies and stable flies within cow patties, a serious problem for cattle. These are just a few examples of how fire ants help us. Perhaps these are not sufficient for us to raise our champagne glasses in toast to the fire ant, but they do provide a positive side to one of our newest acquaintances.
The Sting of the Wild Page 8