Locust (30 page)

But twenty years after Uvarov’s vision of the future, we were still floundering for an explanation. Entomologists typically offered some obtuse arguments about a complex set of large-scale ecological changes involving bison, weather, and fire. Paul Riegert’s contention was fairly typical: “With the relatively fast removal of the bison from the plains, came the quick extermination of
M. spretus
. The cause and
effect relationship may not have been absolute but it certainly was contributory.” That was the best we had, a diffuse assurance that some sweeping environmental alterations had somehow conspired not to just prevent locust swarms but to entirely decimate the last vestiges of the species.

One of my favorite television shows while growing up was
Columbo
. I liked
Mannix
and
The Rockford Files,
too. For that matter, I’ll even confess to having a soft spot for Mickey Spillane stories. My favorite part of
Columbo
was when Peter Falk would seem to have finished interrogating someone and be headed out of the room. He’d suddenly stop, cock his head, turn back to the suspect, and say, “Just one more thing. I was wondering . . .” And he’d proceed to completely undercut the neat-and-tidy alibi of the poor sap. That’s a bit how I felt coming onto the scene in 1986.

I was aware of the various theories regarding the murder of the Rocky Mountain locust. For the scientific community, these explanations were collectively sufficient to consider the case closed. It wasn’t a tidy story, but it was good enough for the inherent uncertainties of a death that had occurred before any of the active investigators had been born. But being the new kid at the scientific stationhouse, I sensed that there were too many loose ends and holes, too much logical leaping and scientific supposing. I didn’t buy the vague story that had been assembled. My own sense was that each of the suspects had a convincing alibi. There was no murderous factor—either natural or human—across the West. You can’t derive the whole truth from an assemblage of half-truths. In my estimation, the case of the Rocky Mountain locust’s disappearance needed to be reopened. But nearly a century had passed since the last individual was seen, there were no living witnesses to provide insights, and two generations of entomological detectives had puzzled over the available information. It’s easy to dismantle someone else’s case—it’s not so simple to build a new one.

A
CENTURY AFTER THE HEYDAY OF THE ROCKY MOUNTAIN locust, the trail of clues leading to the demise of the species had grown cold. No new evidence had surfaced since Ashley Gurney provided the insight that had elevated this creature to a valid, but extinct, species. I had nothing more to work with than the previous generation of entomologists, but the mystery was simply too compelling, the existing “explanations” were just too full of holes, and my desire to build a reputation in my newfound field of study was too intense to let the case go. Of course, as a new assistant professor at the University of Wyoming in 1986, I didn’t bet all of my chips on this one long-shot gamble. I pursued studies of grasshopper feeding, biological control with pathogens, and modeling of population dynamics. But with a sense of adventure and a bit of funding, it seemed that I could pursue at least one line of investigation concerning the Rocky Mountain locust that hadn’t been exhausted—and for a very good reason: The evidence was locked away in ice, two miles above sea level.

A proper—and fundable—grant proposal provides a compelling scientific rationale for the planned research. My proposal to the National Geographic Society included what seemed to be some rather convincing arguments for funding an expedition to what early geologists had come to call Grasshopper Glacier, a magnificent and mysterious body of ice just north of Yellowstone National Park that had attracted western travelers for decades. The most obvious justification for my project was that no entomologist had been to the site in forty years. It also seemed that the condition of a natural phenomenon and national treasure of this sort ought to be monitored. After all, recession had been ongoing since at least 1931, when observers reported a gagging stench emanating from the foot of the glacier, where a four-foot pile of rotting locusts had melted out of the ice. With similar reports in 1952—the last time a scientific expedition had been to the glacier—one had to imagine that this remarkable resource could be in serious trouble and that the chances of collecting the uniquely preserved insects were dwindling.

The frozen creatures were probably ill-fated swarms of the Rocky Mountain locust, but remarkably—almost unbelievably—none of the specimens collected between 1914 and 1952 had made it back to a museum. The only entomologist to examine the icebound insects had been Ashley Gurney, but he had made his observations before he was aware of the differences between the genitalia of
sanguinipes
and
spretus
. So, his identifications indicated that these were the migratory phase of
sanguinipes,
which may well have been
spretus
. If it was the Rocky Mountain locust embedded within the ice, it could represent a bonanza of biological material and sufficient evidence to reopen the case of the creature’s disappearance. Furthermore, there were other Rocky Mountain glaciers purportedly containing frozen grasshoppers, although none had ever been studied by an entomologist. There were specimens of
spretus
preserved in various museums throughout North America, but all of these had been collected in the last few years of the locust’s existence, so they did not represent the species in its vibrant, healthy condition. Perhaps more important, not many specimens existed. A species that once blackened the skies was now a rare scientific commodity.

There are dozens of insect collections in the United States, housed in universities and natural history museums. The largest collection is Riley’s legacy: The National Museum of Natural History contains 30 million specimens, a couple million more than London’s Museum of Natural History. Harvard’s Museum of Comparative Zoology is the largest of the university collections, with 7 million insects tucked away. At the University of Wyoming, we have a modest collection of 250,000 specimens housed in tall, steel cabinets. Looking among our drawers of neatly pinned and labeled insects, you’re likely to find that the largest numbers of specimens represent the most common species.

The closest specimen of the Rocky Mountain locust is seventy-five miles to our south, in the Colorado State University insect collection. Deep in the bowels of this collection, five dried locusts are impaled on pins. Across the continent there are another 482 specimens scattered among half a dozen collections, the majority of these being at the National Museum. For an insect that once numbered in the trillions, this is a infinitesimal record. And to make matters worse, many of these specimens were identified before the definitive anatomical features were known, so a portion of these collections actually could be the migratory form of
sanguinipes
.

As such, we had a rather limited pool of specimens to expend on various tests. Any specimen lost to analysis was an irreplaceable relic of American history and ecology. But there were now powerful—and destructive—analytical methods with the potential to shed light on the nature of the Rocky Mountain locust and the events leading up to its extinction. For example, we had methods of characterizing subtle differences in the proteins of organisms. By passing an electrical charge through a gelatinous film on which proteins of an organism had been placed, it was possible to separate these “building blocks of life” based on subtle differences in their electrochemical charges. Because proteins are made of amino acids, which are the direct products of genes, they can serve as sensitive indicators of genetic differences in populations and species. The problem was that the museum material had been preserved in the standard manner: They were dried specimens mounted on pins. Proteins are like chemical origami, elegantly folded and layered molecules. When these complex chemicals
dry, the bonds holding the folds in place are broken and the integrity of the molecule is lost. This process, called
denaturation,
occurs in the cooking of an egg. The proteins are heated, which causes the original bonds to break and new ones to form, thereby transforming a gooey fluid into a rubbery lump. And it is impossible to reverse the process: Scrambled eggs cannot be turned back into their slimy progenitors. However, tissues frozen for centuries in ice just might be well enough preserved that we could analyze the proteins. And if so, then molecular analysis could be taken a step deeper into the very foundation of life.

I maintained in my proposal that the rapidly developing field of molecular genetics could well provide even more telling clues. If the ice had preserved the insects’ DNA, the chemical blueprint of life, then important questions could be directly answered. We could determine whether the species had been in a long-term decline, with extinction being the culmination of a process that had begun long before human disturbance. Molecular analyses could reveal whether the locust had suffered from inbreeding, causing a genetic “bottleneck.” If we could examine frozen specimens of various ages—and photographs of the glacier clearly showed that there had been layers of locusts at various depths within the ice—it would be possible to detect a constriction in genetic variation. This evidence would strongly indicate that
spretus
had been reduced to abnormally small and isolated populations before dying out. Furthermore, these analyses of the genetic material, rather than bodily structures (including penile oddities), could directly address the fundamental basis for declaring that a life form constituted a true species—the century-old question of
spretus
’s taxonomic status could be definitively answered. And in the 1980s, such investigations required types of evidence that couldn’t be found in museums.

So, to make progress on these fronts, we had to have biological material with three qualities. First, we needed numerous specimens from which to derive representative values. Next, the specimens had to be in a well-preserved state for chemical analyses. Finally, and most important, we needed material that represented the natural state of the locust. To understand what may have happened in the final years of
spretus
’s existence required us to compare its normal, healthy condition
to the biology of the creature in its last dying days. Ideally, we could view both time frames by using well-preserved specimens extracted from the ice, but even if only centuries-old material were frozen in the glaciers, the museum specimens would provide at least some context for assessing the species’ condition at the end of its life.

In addition to providing tissues with these qualities, the glaciers potentially offered a direct window into the locust’s history. If the layers of locusts reported by earlier investigators represented separate depositions over time, then radiocarbon dating could be used to determine when the swarms had lived. In this way, we could know whether outbreaks of the Rocky Mountain locust had been a natural feature of the North American landscape for centuries. Even with Native American accounts, our perspective only extended to the early 1800s. We also hoped to discover whether outbreaks became more frequent with European settlement. Although the theory had been largely dismissed by force of rhetoric, there might have been something to Cantrall and Young’s contention that the irruptions were aggravated, maybe even caused, by human disturbances. Clever arguments and rebuttals are fine, but hard data were needed to refute various theories—and perhaps to develop a viable alternative case.

The grant review panel concurred that Grasshopper Glacier was a fast-disappearing resource. So fast, in fact, that the panel judged my proposal to be a long shot (Gurney’s reports were, after all, forty years old). Disappointed, but undeterred, I scraped together funding from a faculty development grant and the Office of Research at the University of Wyoming. They were no more convinced of my finding frozen treasure, but through later conversations I learned that the decision makers had been drawn into a vicarious sense of intrigue and adventure concerning the mystery of the Rocky Mountain locust and the secrets of Grasshopper Glacier. Such a subjective basis for allocating research funds might seem unscientific and oddly emotional. But then, science is, at its core, a profoundly personal enterprise, irrationally motivated and driven by passion.

 

Perhaps the most wonderfully wicked irony in science is the notion that the clearest vision into the world is provided by a “double-blind”
experiment. In this method, neither the individual measuring the effects of a treatment nor the subject of the experiment is informed of which, if any, treatment has been administered. I was well aware of the ideals of experimental design, as this approach to science was the primary focus of my research program. Although I’d become fascinated with unraveling the story of the Rocky Mountain locust, I had been hired by the University of Wyoming’s College of Agriculture to pursue far more practical matters, such as developing new treatments for rangeland grasshopper outbreaks. In this development research, we sometimes approximate the double-blind design by default. We don’t intentionally keep secret what insecticide was applied to which plot. Rather, as we position thirty or so plots, each the size of forty football fields, on a grassland with few landmarks, it is easy to lose track of what went where. We use plot maps and coded stakes, but it would take a cryptographer or someone with a phenomenal memory to match these with our inevitably arcane coding system. The plot numbers always make sense at the beginning of the summer, but their logic tends to fade with the patina of the prairie as the season unfolds. And as for the subjects of our experiments, the grasshoppers are not informed of which treatment they have received. I sometimes suspect, however, that the condition of their comrades and the declining frequency with which they are encountered leave the insects with a decent picture that something is amiss.