Synopsis
Sometime in the first half of the twentieth century, a coterie of fire ants came ashore from South American ships docked in Mobile, Alabama. They invaded the South, damaging crops, harassing game animals and hindering harvesting methods. The US Dept of Agriculture developed a campaign that failed to eradicate the ants ..
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About the Author
A scholar of the overlap of politics, biology, and ecology in twentieth-century America, Joshua Blu Buhs has written articles that have appeared in Isis, Environmental History, The World of Genetics, and Journal of the History of Biology.
Excerpt. © Reprinted by permission. All rights reserved.
The Fire Ant Wars
NATURE, SCIENCE, AND PUBLIC POLICY IN TWENTIETH-CENTURY AMERICABy Joshua Blu BuhsThe University of Chicago Press
Copyright © 2004 The University of ChicagoAll right reserved.
ISBN: 978-0-226-07981-3
Contents
Acknowledgments......................................................................1Introduction.........................................................................9Chapter One: From South America to the American South, 1900-1950.....................39Chapter Two: Grins a Prohibitive Fracture, 1945-1957.................................81Chapter Three: Fire Ants, from Savage to Invincible, 1957-1972.......................125Chapter Four: The Fire Ant Wars, 1958-1983...........................................171Chapter Five: The Practice of Nature, 1978-2000......................................199References...........................................................................209Index
Chapter One
From South America to the American South, 1900-1950
Out of the night that covers me, Black as the Pit from pole to pole, I thank whatever gods may be For my unconquerable soul.
William Ernest Henley, "Invictus"
The red imported fire ant, noted journalist Charles Haddad in 1990, was not only "a part of the South's ecosystem but" was "embedded in folklore as well." And not just folklore: the ant was a part of southern culture. By the end of the twentieth century the insect occupied about 300 million acres in North America, from Florida to California and as far north as Virginia, an entrenched and ubiquitous denizen of the Sun Belt. Musicians wrote songs about the insect, sports teams used it as a mascot, and the town of Marshal, Texas dedicated an annual festival to it. The ant figured in advertisements, political speeches, and novels. "The fire ant is a swarming, biting nasty little critter whose legend is to flatlands what bigfoot is to the mountains," the Atlanta Journal-Constitution proclaimed in 1986. But this was not always the case. The ant evolved in South America and only came to the American South during the first half of the twentieth century. How did the insect reach North America? And how did it spread and come to dominate the South?
The fire ant's history is a tale of nature, humans, and their interactions. Evolving on a South American floodplain, the fire ant became an adept tramp, able to move easily and exploit open, disturbed habitats. Then, in the late nineteenth and early twentieth centuries, shipping routes tethered its homeland to world markets. Accidentally loaded aboard boats with South American cargo, Solenopsis invicta found itself in Mobile, Alabama, subsequently spreading from the port city across American South. The fire ant's spread, I argue, resulted from the interaction between the insect's biology and human activities. When the imported fire ant reached the United States, American citizens were busily recasting the South's economy and ecology, creating new avenues of transport as well as new open and disturbed areas. The ant traveled along these new corridors and exploited the new habitats. Natural history and human history intertwined to produce the imported fire ant's explosion.
Natural History of the Imported Fire Ants
The imported fire ant belongs to the genus Solenopsis, a group of some two hundred species of ants; only a handful of these are fire ants, about twenty, the uncertainty reflecting the limited knowledge we have of some species. The genus originated in tropical South America around 65 million years ago, as the dinosaurs made their last stand and the Andean orogeny proceeded along the continent's western spine. According to the geological record, Solenopsis underwent an adaptive radiation during the Miocene, before the first Homo sapiens walked across the African savannah. A variety of forms evolved. Some Solenopsis eat seeds; some parasitize other ants. Some live along the littoral, some in treetops, some in subterranean tunnels. Those ants that came to be known as "fire ants" developed a potent sting that gave the group its common name. The humorist Dave Barry remembered that the first time he was stung by a fire ant he "leaped up and danced wildly around, brushing uselessly at my hand, which felt as though I had stuck it in a toaster oven set on 'pizza.'" But while the insects developed different lifestyles, changes in their appearance did not always keep pace. As a group, the ants are rather nondescript, and many species look alike, even to experts. The ant biologist William Steel Creighton wrote that when studying the insects' taxonomy, "[o]ne has the unpleasant feeling that he is entering a battle-field strewn with unexploded missiles and that there is a strong probability that one of these taxonomic duds may, through tampering, bring the investigator to grief."
This confusion clouds the early history of the imported fire ant invasion. For many years, the name "imported fire ant" covered two species, Solenopsis richteri and Solenopsis invicta, both of which journeyed from South America to the American South during the first half of the twentieth century. Solenopsis richteri is a dark brown or black species, with a yellow stripe across its gaster. Solenopsis invicta lacks the stripe of its congener and is red, although sometimes black or brown, too. The two species inhabit different parts of the world's largest wetland, an expanse of marshy land that follows the Ro Paraguay through Brazil, Paraguay, and northern Argentina to its confluence with the Ro Paraa-where the drainage is known as the Ro de la Plata-and, ultimately, to the Atlantic Ocean. The black imported fire ant lives at the southern edge of this riverine system, often in seasonally waterlogged grasslands; it also lives along roadsides in Buenos Aires and amid the grasslands of the drier Argentine pampas. The range of the red imported fire ant runs north from Buenos Aires, following the Paraguay and Paraa into Brazil. The ant also survives on the harsh plains of the Chaco. Solenopsis invicta is the insect now known as the "imported fire ant," the one that has caused most of the problems and has provoked both the South's loathing and pride.
The rivers and their tributaries set the pulse for the ants' South American home. During the dry season, from April to October, rivers run weakly and grasses clog the riverbeds, growing thick in the rich silt deposited by the rivers in years past. When the rains come, and the waters tumble from the Brazilian plateau to the north and the Andes to the west, the tangle of flora forces the rivers to cut new channels. These fill with silt and eventually overflow, flooding the countryside for months. The rivers' vagrancy has created a wealth of habitats and the area supports a rich array of plant life. In 1927 one geographer noted, "The most striking feature in the natural vegetation is its lack of uniformity." 10 Palms stand in swamps; tall grasses dominate savannah-like stretches, while shorter grasses survive on areas that have been more recently covered with water. In parts of the Chaco, quebracho trees grow into forests.
Solenopsis invicta evolved to take advantage of the open and disturbed habitats left in the wake of floods. The entomologist Walter Tschinkel compared the insect to a weed. The ant, Tschinkel said, breeds rapidly, spreads easily, and competes fiercely. A single red queen gives birth to a colony of 230,000 in about three years and produces about 4,000 to 6,000 reproductively viable offspring (called "alates") annually. The alates are produced throughout the year, ready to spread from the nest whenever conditions are right. On clear, calm days after a rain storm, the red alates climb atop the mound then fly away, mating in the air; the males drop dead, but the females fly on, some as far as twelve miles, although most do not cover such a distance. 14 Watching a mating frenzy in the United States during the spring of 1951, an entomologist for the U.S. Department of Agriculture (USDA) was shocked at the ants' "tremendous biotic potential." The ant also uses floods to spread: when waters overwhelm a nest, the colony forms a mass, floats to a dry spot and rebuilds.
Whether alighting after a nuptial flight or borne aloft by floodwaters, Solenopsis invicta settles in any number of environments. It succeeds best, however, in open or disturbed habitats, the kind of places created by the floods and the rivers' retreat. Tschinkel notes, "The fire ant is clearly and dramatically associated with ecologically disturbed habitats.... On the other hand, the fire ant is absent or rare in late succession or climax communities such as mature deciduous or pine forest. When it is found in these communities, it is usually associated with local disturbances such as seasonal flooding and roads." In these exposed areas, the insect protects itself from predators by building large dirt mounds. Its sting is also a useful adaptation for pioneering disturbed environments. The venom produced by fire ants, unlike poisons produced by most other animals, contains alkaloids, chemicals more commonly found in plants. In mammals the venom kills cells; it is also a bactericide, fungicide, herbicide, and insecticide. Many fire ant alates still succumb to predators, but since colonies release so many alates, even if only a small percentage survive the number of colonies in an area grows. The ant's catholic diet also helps it to survive in disturbed areas where food sources are not reliable. Solenopsis invicta eats anything from plants to insects to vertebrates, although it seems to prefer insects and oily foods. (In Mato Grosso, Brazil, locals call the red ant by the Portuguese name toicinhera, derived from the word toicinho-pork fat. There, Solenopsis invicta gorges on the oily nuts of the Bau palm.)
The red ant also seems to have another advantage for colonizing new and disturbed areas: its larvae. Food brought to the nest by workers passes to the larvae, which digest some things that other ants in the nest either cannot or will not. The metabolic by-products of the larvae's digestion are then passed to the queen. If these waste products contain too-low a level of important nutrients, the queen's reproductive output is curtailed: there is no reason to produce young that cannot be fed. Alternatively, some by-products increase the rate at which queens lay eggs. This system allows the ant to calibrate its biology with local conditions, retrenching when resources are scarce and expanding to take advantage of favorable conditions, spreading quickly and easily, like a weed.
While life along a flood plain sculpted the red imported fire ant into the insect equivalent of a weed, Solenopsis invicta is not the only opportunistic member of Solenopsis. Solenopsis geminata, the tropical fire ant, has spread to every continent except Antarctica and Europe, traveling aboard ships and exploiting the disturbed, simplified, and open environments created by humans. It is widely distributed across the southern tier of the United States. Beginning in the sixteenth century, an ant believed to be Solenopsis geminata plagued the islands of the Caribbean episodically; the insect caused so many problems that Spanish colonists considered abandoning Hispaniola and officials in Grenada offered a 20,000 award for anyone who invented a way to exterminate it. In the nineteenth century the English naturalist Henry Walter Bates watched another species of fire ant terrorize the village of Aveyros, on the Tapajos River in the Amazon basin. Years before Bates arrived, martial strife had devastated the area and many had fled their homes. They returned, were driven out by the ant, then returned again, only to see the insect still undermining their village. "The ground is perforated with entrances to [the ant's] subterranean galleries, and a little sandy dome occurs here and there," Bates wrote. "The houses are overrun with them; they dispute every fragment of food with the inhabitants." The ant, he said, was "a greater plague than all the other [insects] put together" and because of them "all eatables are obliged to be suspended in baskets from the rafters, and the cords well soaked with copaba, which is the only means known of preventing them from climbing. They seem to attack persons out of sheer malice."
For the villagers, the ant symbolized the ruins on which their city was rebuilt, the past come to life. The locals, Bates wrote, believed "that the hosts sprang up from the blood of the slaughtered." The connection between the war and the ant must have seemed especially strong since the ant rarely moved beyond the borders of the village. Aveyros occupied a small clearing, hemmed in a by a thick, dark tropical forest. Preferring the open disturbed habitat to the tightly interwoven ecological community below the jungle canopy, the ant was found only in the village and along the sandy shores of the river, where the war had raged and the dead had lain upon the ground.
Bates recorded his observation in The Naturalist on the River Amazons, published in 1863. The book became a classic of adventure and natural science, read throughout the Anglo-American world. This ant, Bates implied, was the antithesis of civilization, growing up in its absence, challenging its return. Bates's judgment was reflected in the insect's name. The traveler captured some specimens of the offending ant and sent them to the British Museum in London, where they were pinned, placed in a collection, and studied. The ant was dubbed Solenopsis saevissima: savage fire ant.
From South America to the American South
As Solenopsis saevissima terrorized Aveyros and Solenopsis geminata tramped around the globe, Solenopsis richteri and Solenopsis invicta remained confined to South America. How did they reach North America? Their passages went unrecorded, but the history can be pieced together. The reconstruction shows that while the ants' biology mattered, it only partly explains their later success: the explosion of fire ants across the American South depended on human commerce and, it seems, the accidental introduction of another insect into the area as well.
Much of the area occupied by Solenopsis richteri and Solenopsis invicta is uninviting to humans and remained lightly occupied into the nineteenth century: during the dry season when the floods recede and the rain stops, rivers dry to a trickle and water is scarce, found mostly in brackish pools. Daytime temperatures climb over 100F and at night mosquitoes materialize out of the grass. "Few areas have a climate so extreme and unforgiving that visitors regularly use the word 'hell' when describing it," commented science writer Erich Hoyt in 1996, but the South American interior deserved the name. Increasing familiarity with the area during the Paraguayan War (1864-70), though, drew people to the area, and an influx of European immigrants also helped to extend agriculture and cattle ranching into the hinterlands of Brazil and Argentina. Railroads stretched from Buenos Aires, Rosario, and So Paulo into the swampy continental interior: between 1895 and 1914, for example, Argentina laid over twelve thousand miles of tracks and cargo weight increased from 5 to 40 million tons. Quebracho trees provided fuels for trains and tannins to cure cowhides into leather. Other construction projects made the harsh climate habitable. Irrigation canals, swamp draining, and dams controlled the mosquito population, assured the permanence of pasture, and provided a steady supply of fresh water. Farmers sowed fields with tobacco and cotton.
Over time, Argentina and Brazil became two of the world's leading beef-producing countries. In the late nineteenth century, Argentineans had shipped live cattle to Europe and America. After a long voyage, however, the animals arrived sickened and weak; few sold. An outbreak of hoof-and-mouth disease among the Argentinean herds around the turn of the century forced changes in the industry. Argentineans started sending the beef frozen or in cans, making shipping less risky. They also imported blooded cattle from England and France to better meet the tastes of their consumers. As a result of these changes, the industry boomed. By 1935, Argentina provided over half the world's beef. Meanwhile, World War I prodded the growth of Brazil's cattle industry. Frozen and chilled beef exports grew from 1.5 metric tons in 1914 to 65,000 metric tons in 1917.
The railroads, farms, and ranches imposed a new ecological order on the region, one that operated not according to the rhythms of the wet and dry seasons, nor in step with the pas de deux danced by the region's hydrology and botany, but according to human imperatives. New species thrived-cattle, grasses imported to feed the animals-while the populations of some plants and animals long established in the region struggled. But while humans had created the system, they were not always in control: humans change nature, but nature always remains more complicated than humans know, and the manifold consequences of our actions are impossible to fully predict. Thus, the ships that visited the port cities of eastern South America carried not only cattle and agricultural goods to the world market, but Solenopsis richteri and Solenopsis invicta as well, travelers that no one saw or imagined.
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Excerpted from The Fire Ant Warsby Joshua Blu Buhs Copyright © 2004 by The University of Chicago. Excerpted by permission.
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