Locust (19 page)

The survey’s goal was to assess the agricultural resources of the western territories, and this objective offered Thomas the opportunity to demonstrate his intellect and integrity. Despite ardent claims by land speculators, Thomas argued that there was simply too little rain to sustain crop production throughout much of the country west of Iowa and Missouri. But unlike Riley, who loved nothing better than publicly refuting an opponent, Thomas was almost apologetic in his assertion that promoters had been painting a deceptively rosy (or verdant) picture of the Great Plains: “I dislike to make such statements, but I deem it my duty to speak plainly on this point.” Such truthfulness put him in good stead with Hayden, who valued scientific objectivity. Consequently, when the opportunity arose to form an Entomological Commission, Thomas was well positioned to take an active role in politicking through the Department of Interior.

So it was that a European artist-turned-farmer/writer-turned-entomologist teamed up with a Harvard zoologist-turned-physician-turned-entomologist and a country-lawyer-turned-minister-turned-entomologist to form the first U.S. Entomological Commission—one of
the most formidable teams of scientists to ever tackle a problem of the natural world. But first, they had to tackle their own problem: how to work together. The solution was as practical as the task before them. They’d simply divide the country into sectors and go their separate ways, coming together only when necessary to exchange information or conduct business. Riley would serve as the chief, which meant that he would be the spokesman and play the central role in drafting and editing the commission’s reports and recommendations. Not only did he covet the mantle of leadership, but his lack of attention to administrative details and his propensity for financial expediency made the roles of secretary and treasurer highly inappropriate. This arrangement seemed to suit Packard and Thomas just fine, as they were happily occupied with their travels and studies. They viewed the venture as a wonderful scientific expedition and a substantive contribution to the nation. Being neither naive nor altruistic, both would parlay the experience into ascending careers in science. However, neither saw the venture with the political acumen of their extraordinarily ambitious leader. Only Riley had the vision to leverage his position into one of truly impressive power and national influence.

Riley’s cardinal principles in guiding the work of the commission were succinctly summarized in the opening paragraph of an early report: “Knowledge is power in protecting our crops against the ravages of a tiny insect, as in all other undertakings; and according as accurate knowledge regarding this locust plague is disseminated among our people, will they be able to vanquish the common foe.” Never before had such a systematic and rigorous scientific approach been taken to a complex environmental or agricultural problem. The breadth and depth of the commission’s work is difficult to summarize, involving everything from beautifully rendered drawings of the locust’s internal anatomy to massive tables of climatological data pertaining to the insect’s outbreaks. However, the trio’s greatest impact on science and society clearly lay in the dual capacity to debunk erroneous notions about the locust and to reveal new insights into its biology. Of course science had been making discoveries about the world’s flora and fauna
for many years, but the commission’s breakthrough was in converting natural history into practical knowledge—knowledge that could be used to formulate effective strategies for altering ecological processes. In short, the commission’s work demonstrated that the field of ecology—a term coined in 1869 by Ernst Haeckel, a German biologist—could provide a powerful foundation for modern agriculture.

Riley and his colleagues made a series of fundamental discoveries that set the stage for developing effective control methods. The commission pioneered the practice of “integrated pest management” (IPM), a strategy in which complementary control methods are used synergistically to prevent or suppress pest outbreaks—and a method that was supposedly “discovered” a century later (when, in fact, the unoriginal practice was merely given a clever name and acronym) as entomologists realized that sole reliance on insecticides was doomed. Some of the commission’s revelations are so readily apparent to the modern entomologist as to be overlooked in their importance, until we realize that such facts were far from obvious more than a century ago.

For example, much of the public believed that the Rocky Mountain locust was the same insect that had plagued farmers of the Old World for millennia, therefore presuming that whatever interventions had worked in other times and places were appropriate for the present onslaught. Moreover, it was commonly held that any grasshopper reaching high densities anywhere in the United States was the nefarious locust. After all, if the beast had crossed an ocean to reach the New World, surely its distribution would not be constrained within North America. Riley and his colleagues were able to show that the Rocky Mountain locust was unique to this continent, being taxonomically distinct from the locusts of Africa, Asia, and Europe. Furthermore, they convinced farmers and others that the grasshopper outbreaks in Georgia, South Carolina, and New England were not the work of the Rocky Mountain locust. These infestations had entirely different origins and required fundamentally different responses. Indeed, what we now accept as the common name of the locust was assiduously defended by the commission against other alternatives. Riley felt strongly that the species’ name should reflect its biogeography and thereby remind the public of the creature’s origin.

Biogeography arose as a scientific venture with the capacity of nineteenth-century European explorers to travel the globe and catalog the world’s flora and fauna. Driven by curiosity and economics, these expeditions—the most famous being Darwin’s voyage on the British survey ship the
Beagle—
revealed striking patterns in the distribution of living organisms. The ability of the U.S. Entomological Commission to travel the West by rail and horse provided these entomological explorers with the mobility necessary to map the distribution of the Rocky Mountain locust. And what they found was tremendously important. Riley and his commission were able to document the origin of the locust’s outbreaks within the area that they designated as the Permanent Zone. They also traced its migration circuit (from the mountains into the plains and back again over the course of several generations) and its ecological limits. Contrary to impassioned cries that the locust would overrun the country, the entomologists showed that the swarms invariably petered out near the Mississippi River. As Riley noted:

Fundamental discoveries of the locust’s population dynamics also repudiated other prevalent misconceptions about causes of the creature’s outbreaks. Fallacious reasoning had given rise to the prevalent notion that droughts were caused by prairie fires set by settlers to clear the land for planting. In turn, the dry air allowed the Rocky Mountain locust to fly easily through the atmosphere and extend its depredations into the Great Plains. Based on these notions, legislatures considered laws prohibiting farmers from setting fire to the grasslands. Riley argued that the cause-and-effect sequence was entirely mistaken. Rather than fires causing drought, drought created the conditions that fostered
both natural and man-made fires. Furthermore, his studies showed that locust flight was not extended by a parched atmosphere but that the hot conditions during a drought created longer periods during the day in which the cold-blooded creatures could sustain activity. The commission maintained that outlawing the burning of prairie grasses would have little effect on suppressing the locust—indeed, quite the opposite. They advocated burning fields where the locusts had laid eggs to deprive the hatchlings of food.

Even the locusts’ behavior was the subject of misunderstandings, which might well have led to absurd management practices if not refuted. The entomologists found that, contrary to popular opinion, the bands of immature nymphs were not led by “kings or queens,” nor were their movements governed by large “guide locusts.” Had such an insectan command structure existed, then the bands could have been dispersed or sent into chaos by the strategic destruction of their leader—and considerable resources would have been wasted in such a misguided effort. Riley discovered that the nymphal bands were leaderless mobs, orienting to one another and to environmental cues. What farmers presumed to be guide locusts were simply the brightly colored adults of an earlier-hatching species that sometimes exploited the same fields as the locust nymphs.

Understanding the locust’s biology also allowed the commission to narrow the time and space into which management practices could be most effectively concentrated. The widely held belief that females could lay only a single pod of eggs had led to understandable confusion as to how so many locusts could hatch from the fields after a swarm had passed through. By proving that females could lay more than a single pod of eggs—thereby potentially increasing the locust population 100-fold from one generation to the next—Riley was able to account for the startling reproductive capacity of the locust. Moreover, knowing when and where eggs were laid, what time of year hatching commenced in various locales, and the distances that the nymphs moved before fledging set the stage for a scientific approach to control.

The commission understood that although the most spectacular phase of the locust was the swarms of adults, the creature was virtually
unassailable at this time. No amount of frantic beating, or acrid smoke could avert a descending swarm. The key lay in the locust’s least conspicuous and most vulnerable life stage—the egg. The entomologists knew that the sedentary eggs could be subjected to systematic assaults for months on end. Riley conducted extensive and elaborate experiments on how moisture, temperature, and soil properties could reduce the survival of eggs. Although these laboratory studies were often flawed in their design, Riley made up for his lack of formal scientific training through keen observations in the field. These real-world assessments were sufficient to demonstrate that plowing, harrowing, and flooding the locust’s egg beds were not simply ways of flailing at the egg beds and giving farmers a sense of “having done something” but were the ecological key to quashing an outbreak. Riley was also a staunch supporter of the bounty system for eggs, arguing from his research that for every bushel of eggs that was destroyed, 100 acres of crops could be saved. The widespread adoption of these ovicidal tactics and bounties can be largely attributed to the commission’s work.

The commission advocated the widespread use of ditches to control the nymphs before they could become swarming adults. Understanding the labor involved, the entomologists studied the efficacy of various configurations and developed what became the standard set of dimensions for a ditch that would minimize the amount of digging while maximizing the rate of trapping. Even so, the commission realized that the scale of trenching was beyond the capacity of many frontier communities. Alluding to the use of the army against locusts in Algeria and France, Riley pressed hard for the use of the military in providing labor to suppress the locusts. At the 1875 meeting of the American Association for the Advancement of Science in Detroit, Riley laid out his case for using the army to “carry the war into Africa”—that is, to take the battle into the locust’s native land in the Rocky Mountains. Although federal troops were never mobilized, the commission’s position supported state legislation allowing conscription for “locust armies.”

The entomologists were rather less enthusiastic about various contraptions for controlling locusts, as their efficacy and expense were
rarely justified. The commission’s chief, however, managed to parlay the farmers’ entrepreneurial fervor into a bit of notoriety for himself. The “Riley Locust-Catcher” became perhaps the best known of the machines, courtesy of a rave review in an early issue of
Scientific American
: “Professor Riley, of the Entomological Commission, perfected last summer a grasshopper machine, which seems to be just the thing.” It was, in fact, a hybrid of components drawn from other devices. He had the further savvy not to patent his machine—assuming that it was sufficiently novel to warrant this protection. Such legal niceties were marginally enforceable and economically worthless on the frontier. Moreover, Riley could gain far more in terms of status and public acclaim by generously offering his device to the besieged farmers, and not exercising his putative right to patent “unless it should be found necessary to prevent others from doing so.”

The commission enthusiastically endorsed the use of biological control for suppressing the locust. They clearly understood that the greatest natural mortality was through the action of various unheralded parasites—mites, flies, and beetles—that ravaged the locusts. Although they could not see many opportunities for enhancing or augmenting these tiny allies, their studies of the locust’s ecology laid the foundation for our modern methods of biological control that emphasize the use of host-specific parasites and pathogens. Without the technical means of rearing and releasing biological control agents, the commission turned to the conservation of locust predators. In this context, their reports provided a bully pulpit for Aughey’s earlier work and the political leverage to impel the passage of legislation protecting native birds. Much to his credit, Riley shied away from calls to intentionally spread exotic species, such as the English sparrow. He maintained that this bird was unlikely to consume many locusts and that if it could thrive in the locust’s range, then it would spread there on its own. As an ecologist, Riley seemed to intuit the risks of invasive, nonnative species to natural and agricultural landscapes, a prescience that unfortunately has not been widely shared by economic entomologists even into recent times.