Locust (37 page)

The life cycle is repeated in late spring or early summer, giving rise to the grandchildren of the Mexican population. These monarchs extend the range of the species into southern Canada. In summer, the adult butterflies survive for a month of hedonistic activity, dividing their time between mating and sipping nectar. By mid-summer the great-grandchildren appear, and in late summer the great-great-grandchildren make their debut. However, this last generation is a radically different population. In response to cooler temperatures and shorter days, the adults alter their physiology and behavior. They are like overtrained athletes; their reproductive organs fail to mature and their libido is suppressed. These insect Olympians stock up on high-energy nectar and then begin the long, arduous return migration to Mexico. After four generations, the population of monarchs has grown tremendously, but the 2,000-mile journey takes a brutal toll. More than 200 million butterflies may begin the return migration, but just 1 in 100 makes it to the wintering grounds. How they find their way back to the home of their great-great grandparents remains a mystery.

The winter sanctuaries of the monarch were not discovered by scientists until 1975, although local villagers had known the butterfly’s secret for many years. The monarchs spend the winter in patches of fir forest west of Mexico City, clustering at perhaps a dozen small sites on the southern slopes of the mountains. Imagine having 35,000 monarchs in an area the size of your living room. Hang 700 decks of playing cards from your ceiling, walls, and furniture if you’d like to get a better impression of these aggregations.

For five months, these butterflies remain virtually immobile, blanketed by the cool, damp forest and insulating one another from the rain and snow that leaks through the canopy of trees. During the long winter at nearly 10,000 feet they rely almost exclusively on their fat reserves. Predators often take one in ten of the butterflies overwintering in a colony, but a harsh winter is perhaps the greatest threat, with as much as 80 percent of a colony succumbing to a bitterly cold, wet storm, as happened in 2002. With the spring thaw, the butterflies stir and begin their northward migration. The population again begins to grow at a phenomenal rate, individual females laying 400 or more eggs.

Monarch population dynamics are reminiscent of a roller-coaster ride. In recent years, the population dropped precipitously, a change that triggered great concern for the future of the butterfly. Conservationists have sounded warnings regarding large-scale alterations in the monarch’s habitats. It doesn’t bode well for a species whose only food—milkweed—is, after all, a weed. As roadsides are increasingly mowed and sprayed, the monarch’s larder is depleted. There remain, however, large untended tracts of milkweed, so the decline of this plant doesn’t represent an imminent threat to the butterfly. Likewise, the environmental alarm over the contamination of milkweed patches via genetically engineered crops now appears to be rather premature.

Although continental-scale hazards afflict the monarch throughout the summer, most entomologists have focused on the time and space in which the species is most vulnerable—the ecological bottleneck of its overwintering sites in Mexico. In 1986, a Monarch Butterfly Biosphere Reserve was created to protect the butterfly’s roosting grounds. However, this decree simply mandated protection without offering the local landholders, who are economically dependent on logging, any alternative or compensation. Not surprisingly, deforestation in this area has continued, so that nearly half the original forest habitats that harbor the butterflies have been lost since the reserve was created. To make matters worse, the quality of the remaining forest is rather poor from the insect’s perspective. The economic demand for low-quality wood to produce particle board means that loggers take the young trees that can be readily converted into wood chips. The result is an excessively thinned forest that provides little protection against the weather for the overwintering monarchs.

But as grim as the prognosis may be, the situation could be even worse. The butterflies are concentrated into a dozen or so colonies that occupy only a tiny fraction of the forest during any winter. Between November and March, the quiescent colonies are extremely vulnerable to disturbance. If, by chance or malevolence, the loggers were to cut down the groves being used by the overwintering monarchs, the results would be devastating. Just three dozen loggers armed with chain saws could destroy the entire population of monarchs in the course of a single winter. North America would be left with only a small western
population of monarchs that primarily winters along the California coast and comprises about 5 percent of the total.

The take-home lesson for my students, in addition to the various implications for mathematical modeling, is that a population is only as safe as its weakest link. An ecological bottleneck can spell disaster for a species if the compression of its numbers occurs in a time and place where human disturbance is likely to occur. If twenty-second-century textbooks in insect ecology recount the disappearance of the monarch butterfly, the story will most likely center on a small tract of forested mountainside in Mexico—not in the fields and roadsides of the North American continent.

 

For some people, epiphanies arrive on bolts of lightning, forever changing how they view the world. Religious transformations are among the most spectacular of these changes. The classic story in this regard is the conversion of Saul, who is now better known as Saint Paul. While riding to Damascus, where he was intending to obtain authorization from the synagogue to arrest Christians, Paul experienced the most unambiguous of epiphanies. The poor fellow was struck to the ground, blinded by a heavenly light, and heard the voice of God cry out, “Saul, Saul, why do you persecute me?” His attendants, who also heard the Almighty, led him the rest of the way to Damascus, where the voice said he would receive further instructions. And the rest is history.

I can’t recall that there was an astonishing moment of “Eureka!” or a sudden realization of an impending breakthrough in the case of the Rocky Mountain locust. I do, however, remember long hours of meandering conversations with Larry DeBrey in the cab of a Chevy pickup crossing the austerely beautiful steppes of Wyoming in the course of our summer research on grasshopper outbreaks. And one of our mobile discussions has crystallized in my memory as the turning point in the investigation.

The otherwise unremarkable afternoon involved a coffee-infused discussion that took place in Old Blue—the peeling, rattle-trap truck that we still use in the field. The conversation—in equal parts intended to keep me awake at the wheel and to pass the time pleasantly—wandered around one of our favorite topics, the case of the locust’s
disappearance. We talked on and on, sipping bad-but-free coffee from the gas station in Medicine Bow and touching on elements of Western history, pioneer agriculture, grasshopper ecology, and other cases of extinction, in no particular order. Somehow, the conversation began to swirl around the embattled status of the monarch and the final retreat of the locust. What had been an erratic flitting of loosely connected ideas circled toward a point of mental illumination. Given that I was driving at about eighty miles an hour, it’s probably good that the epiphany was more like a slowly unfolding dawn than a rapturous bolt of lighting.

“What if,” I asked, “we’ve been looking at the wrong scale for all these years? What if the locust died out in the same way that the monarch is likely to disappear?”

“Yeah, could be.” Larry replied, not being one to be knocked from his horse by epiphanies—either divine or secular. “A few pioneers might’ve done a lot of damage by logging, mining, and farming in the locust’s Permanent Zone.”

“When we get back,” I went on, “dig into the library and see what you can find on European settlement in the Rocky Mountains. We need to figure out what the pioneers were doing when the locust was declining.”

“They may not have been the sharpest crayons in the box,” Larry replied, “but I’ll bet they must’ve headed to the river valleys, where there was water and decent soil.” He penciled a reminder to himself in the ragged notebook that he kept on the dashboard.

“Smarter than Laramie gardeners, eh?” I replied. We had both tried to grow vegetables back home. Although he was far more successful in this venture, we had a running joke that at 7,200 feet on the high plains of Wyoming, the only things standing between us and our bounty were water, soil, and heat.

“Ah, hell,” he said after a contemplative pause.

“What’s wrong?”

“I forgot to tell Deanna to water the tomatoes. They’ll be shriveled like an Eskimo’s scrotum when I get back.”

Our conversation digressed into various aspects of gardening, women, and life in Laramie. The road wasn’t leading to Damascus.
The epiphany was simply tucked away for consideration after we were back on campus. Sometimes a revelation comes with a flash of heavenly light and a booming voice—and sometimes it is jotted in a sun-bleached spiral notebook.

 

Between the tattered leather covers of the first three reports of the U.S. Entomological Commission lie 1,258 pages of text, tables, and drawings concerning almost every imaginable aspect of the Rocky Mountain locust. There are weather charts detailing the prevailing winds, average temperatures, and typical rainfalls; there are lists of outbreaks subdivided by states and years; there are tables of locust body measurements broken down by locations; and there are woodcuts of locusts, their natural enemies, and various contraptions meant to control these pests. Scattered throughout the pages are dozens of plates, illustrating everything from the histology of the brain, to the cellular structure of the gut, to the rectal tissues of the locust. The appendices are filled with detailed accounts of the locust’s invasions from across the nation, all meticulously rendered in hundreds of pages of seven-point font. Best of all are the gorgeous maps, including a color-coded, six-panel foldout map in the Second Report that covers an area of thirteen square feet. Supplementing these tomes are Riley’s annual reports to the state of Missouri preceding the commission and various reports that he made to the U.S. Department of Agriculture following the work of the commission.

These volumes are packed with information, the overwhelming majority of which pertains to the biology, ecology, and management of the locust during its outbreaks. This, of course, makes perfect sense. We are captivated by stories of heroes and wars, corporate giants and cataclysmic deluges. Who would write a book about mild personalities or minor battles, and who would want to read a report of a typical business or an average thunderstorm? I had been reading accounts of the locust with the eye of a thrill seeker, relishing the dramatic descriptions of swarms and ensuing battles. But now my goal was precisely the opposite.

While Larry was digging through Western history, census figures, and government reports, I began to scour the entomological archives for
evidence of the locust’s life between outbreaks. Rather than trying to picture the locust at its peak of vitality, I set out to glean the information necessary to reconstruct the life of this creature at its most vulnerable, when the insect was confined to its sanctuaries in the Permanent Zone. Ironically, this time of recession probably accounted for 80 percent of its life history, but only a small fraction of the texts was devoted to how this creature spent its life in the land for which it was named.

The modern world is drowning in information. We have more data than we can possibly use regarding nearly every picayune matter of society, economics, and politics. Science has contributed to this tsunami of facts and figures, but Riley’s reports demonstrate that the tidal wave of minutiae is hardly unique to our time. In every age, the challenge has been to move from information to knowledge. And the value of experts lies in their capacity to extract meaning from the reams of facts. Rather than being swamped by raw data, the connoisseur, artist, craftsman, engineer, clinician, or scientist is selectively and self-consciously blind. Knowing what to ignore, recognizing what is extraneous, is the key to deriving pattern, form, and insight.

A meticulous rereading of the various reports and documents from the late 1800s concerning the lives of locusts and humans initially unearthed only scattered clues, but soon the puzzle pieces began to link together and form a clear picture. From the evidence that could be gleaned from these yellowed, crumbling pages, a single startling conclusion emerged. The unmistakable identity of the locust’s killer slowly took shape—and the perpetrator of the most spectacular extinction event in the continent’s history had not even been a suspect in the century following the locust’s disappearance. Making such an audacious case in the court of science would hinge on three essential lines of evidence. Just as in a criminal trial, I would need to show that the accused had the opportunity, the means, and the motive to perpetrate the killing.

According to Frederick Jackson Turner, a noted historian, the quality of America that distinguished the nation from its European cousins was the process of settling the frontier. A little more than a century
ago, one of the greatest migrations in human history was coming to a close. Nearly 2 million people moved to the western prairies and mountains in the 1870s. In modern terms, this would be equivalent to seeing Colorado, Idaho, Montana, Nevada, New Mexico, North Dakota, South Dakota, Utah, and Wyoming grow from empty lands to their current populations. That many folks streaming into a region in a matter of ten years would have tremendous ecological and economic repercussions.

With the financial panic of 1873, thousands of people had been thrown out of work in the East, and the promise of free land and a new start drew homesteaders to the West as surely as locusts poured out of their crowded and dwindling montane habitats during a drought. The industrialists were delighted, as the western migration drained the unemployed from the restive cities. Many folks believed that the rain would follow the plow or the trains. Respectable scientists (such as Harvard’s Louis Agassiz), less than credible professors (such as Nebraska’s Samuel Aughey), and disreputable journalists explained that the aridity of the plains would be converted into lush fields because “the concussion of the air and rapid movement produced by railroad trains and engines affects the electrical conditions of the atmosphere.” Within little more than a decade after the locusts declined, the populations of Colorado and Nebraska doubled, and those of Montana, South Dakota, and Wyoming tripled. Between 1870 and 1900, as much land was settled and brought into agricultural production as had been transformed in the previous 250 years of North America’s history.