Locust

by Jeffrey A. Lockwood

  After returning to my lab in Laramie, I laid out the five mandibles, like chips of polished ebony. “That’s it?” asked Scott Schell, one of my graduate students at the time. He had a keen sense of the time and expense that had gone into getting these tiny structures.

  “Yeah,” I replied, “not much to work with, is it?” I didn’t want to figure out the cost per ounce of the material from this expedition.

  “Well, I don’t know,” he answered, “Wasn’t there a paper back in the 1940s where some guy associated mandibles with feeding preferences in grasshoppers?”

  “That’s right,” I replied, the wheels starting to spin. But Scott was ahead of me.

  “If mandibles differ enough to distinguish what types of food a grasshopper eats, then maybe they could also tell us what species they came from,” he offered.

  Zoologists often rely on teeth to differentiate species of mammals, and dental records are a standard method for identifying human remains. Nobody had ever tried to use insect mandibles in this manner, probably because it would be crazy to extract these structures for taxonomic purposes when the insects had such wonderfully varied and readily accessible legs, wings, antennae, and other features. The grasshopper’s mandible is very much like a tiny molar, used for grinding its food. We had also found a lacinia, a hardened, scythe-like mouthpart used like our incisors to cut pieces of leaves from a plant. However, we’d found only one of these, and the lacinia is not as elaborately sculpted as the mandible. Scott made a series of fine measurements of the mandibles from a range of grasshopper species, including four specimens of spretus that the curator at the University of Nebraska was kind enough to allow us to extract from his precious charges. With the statistical assistance of another of my graduate students, Chuck Bomar, it was soon evident that forensic dentistry was a bizarre but effective approach to sorting out grasshopper species. The mandibles from Grasshopper Glacier matched those of spretus, whereas all of the other species were clearly separate and distinct. Excited by both the discovery of spretus (as far as we could determine) and the development of a unique method for identifying grasshopper remains, we submitted a manuscript for publication.

  Although the paper was accepted, my colleagues were clearly unimpressed. With this third paper on glacial remains claiming that the ghost of spretus was seen in decomposed remains dug from icy graves, the reviewers made acerbic reference to my lab having yet again “found” the long-lost locust. The sense was that our objectivity was compromised by our devotion to the search—that we were looking so hard that we were destined to see the Rocky Mountain locust whether it was really there or not. The reviewers begrudgingly accepted the use of mandibles as a means of identifying the grasshopper remains, insisting that we restrict our conclusions to the narrowest possible interpretation—that we had found mandibles more consistent with those of spretus than with those of the other species examined in our analysis.

  We’d gained a small victory by having our latest work published, but it was evident that the scientific community was not going to tolerate any more discoveries of rotting and fragmented insects from glaciers. As one reviewer tersely noted, “This paper only warrants a very short note. . . . The authors already have five articles on these grasshoppers.” If we wanted to claim that glaciers of the West harbored a hidden biological treasure, then a few flecks of gold were not going to cut it. We had better find the mother lode—intact and unambiguous specimens of the Rocky Mountain locust—or drop this crazy treasure hunt.

  12

  The Mother Lode

  WHILE WE WERE SCOURING THE GLACIERS FOR biological treasure, other scientists were documenting their disappearance. The largest concentration of glaciers in the American Rocky Mountains is found in the Wind River Range of western Wyoming, and seven of the ten largest glaciers in the Rockies are nestled among these rugged peaks. These storehouses of frozen water are the aquatic savings accounts for thirsty agricultural enterprises downstream. Although the precise contribution of these ice fields to the region’s water supply has not been fully determined, we know that runoff from just two of the sixty-three glaciers accounts for nearly a tenth of the flow into the Wind and Green rivers. These watercourses are the lifeblood of hundreds of farmers with irrigated fields of sugar beets and alfalfa. In recent years the annual snowfall in the mountains has been inadequate to fill the rivers, so glacial meltwater has become increasingly important, especially in late summer and early fall, when the previous winter’s snowpack has disappeared.

  Consuming these ancient stores of water is the equivalent of a business constantly drawing on its capital. There will come a time when the water bank—the high mountain glaciers—runs dry, and irrigated agriculture will evaporate. These glaciers are receding at a rate of 10 to 40 percent each year, and no fund can long withstand such a rate of depletion. Dinwoody Glacier is the second largest glacier in the Wind River Mountains, and the account of its recession is profoundly sobering. The amount of water remaining in this glacier is equal to that which was lost between 1958 and 1983. If this rate of retreat continues, the glacier will disappear in about twenty-five years.

  Such worrisome figures have generated intensive studies of the glaciers, as scientists attempt to forecast the loss of these vital resources. A geologist and a hydrologist from the Water Quality Laboratory at Western Wyoming Community College in Rock Springs have spent years monitoring Knife Point Glacier, a sweeping expanse of ice that is part of a string of ice fields stretching for ten miles along the continental divide. This complex comprises the largest store of frozen water in the United States, including the two largest glaciers in the American Rockies. Craig Thompson, the laboratory’s director, is a vibrant fellow with an irrepressible sense of curiosity. He is a consummate organizer and made the logistical nightmare of the twenty-five-mile treks into the glacier possible. His partner, Charlie Love, is the son of Wyoming’s most famous geologist, David Love, immortalized in John McPhee’s Rising from the Plains. Charlie is a weathered and irascible fellow who looks as if he’s probably been “nearly sixty” for a good many years. He is an accomplished geologist, but he is best known for his anthropological work on Easter Island. In 1987, when we were on our first trip to Grasshopper Glacier outside Cooke City, Craig and Charlie had chipped loose a couple of softball-sized hunks of ice from Knife Point Glacier. They were intrigued by the composition—the samples were encrusted with insect parts.

  Wyoming has been described as a “small town with very long streets,” a reference to the fact that with only 490,000 people there is a statewide sense of being a community—and news manages to find its way throughout the populace. So it was not surprising when I received a call from Craig shortly after our return from the glacier in 1989. He said that he’d read my papers about the search for the Rocky Mountain locust and that Charlie could give me their frozen blocks of insect remains on his way through Laramie in a couple of weeks. I knew from the moment Charlie lifted the first frozen block from the cooler that this had the potential to be the mother lode we’d been seeking. The ice looked like something that had been chipped from a filthy roadside days after a snowstorm. But rather than pebbles, twigs, and trash, the ice was blackened with grasshopper—or locust—parts. Legs and wings were packed into the most wonderful crusty mass of frozen detritus that I’d ever seen. I thanked him profusely (never had such gratitude been offered for such an ugly gift) and promised to call him with the results of our extraction.

  After thawing, the smaller block of ice yielded just two ounces of dried matter. But from this scant material we managed to harvest more than a thousand grasshopper mandibles. This was easily the richest deposit that we’d encountered since beginning our research. However, within the larger chunk we found a biological gem—the intact bodies of two grasshoppers or locusts. Although the bodies were horribly crushed and twisted, they were undeniably in the genus Melanoplus. Upon ever so gently teasing away the accretions of grime and silt adhering to the abdomens, we found that both were femal
es. We had found what was likely to be the treasure chest, but the key was missing! The various measurements were all consistent with these being Rocky Mountain locusts, but without the male genitalia we could not be absolutely certain. There was only one course of action. We began to make plans to join Craig and Charlie the next summer on their trek to Knife Point Glacier.

  In the intervening months, we obtained radiocarbon dates for the specimens. The deeper deposit yielded an age of 400 to 500 years, and the shallower collection site provided material that was 150 to 250 years old. We now knew that the mutilated females had become embedded in the ice when the Rocky Mountain locust was alive, so the motivation to reach the glacier became all-consuming and the winter dragged on interminably. To make matters worse, plenty of snow was falling. The possibility that the summer melt would not uncover the ice at 12,500 feet was a miserable prospect.

  Spring comes late in Laramie, snow flurries being a tradition during the university’s commencement exercises in mid-May. Given the cost and effort needed to trek from the outfitter’s lodge to the glacier, Craig and Charlie had learned that investing in a reconnaissance flight by small plane was a wise strategy. But there was no point in even looking for a window of opportunity until August. So, through the summer, we conducted our research on rangeland grasshopper outbreaks in the balmy conditions of the Platte River valley, just a couple hours east—and 3,000 feet lower than—Laramie. Roasting in the 100-degree heat near Wheatland, Wyoming, in July, we could look forward to the possibility of frosty nights that loomed just one month later and nearly two miles higher. In early August we got the call from Charlie: “Our flyover yesterday came off without a hitch. Patches of ice are showing through, so we should plan to be on the glacier within a couple of weeks. You guys ready to go?” We’d never been more ready for an expedition.

  Gary and Sue Weiss were tremendously hospitable outfitters, feeding us huge slabs of prime rib the night we arrived at the lodge and regaling us with stories of harrowing trips and wild adventures. In the morning, they supervised the packing and saddling of the horses. Our wrangler, a rather sullen but seemingly competent fellow, mounted his horse and led us from the lodge before the sun had peeked over the ridge. The day was clear and we made good time for the first twenty miles. Then the trail deteriorated as we climbed through alpine meadows. The wet rocks and muddy quagmires fed by the last of the melting snowbanks made for treacherous riding conditions. After nearly seven hours on a horse, hiking the last five miles was a relief and gave my legs a chance to stretch in more accustomed ways.

  We camped on lush, spongy tundra about a thousand feet below Indian Pass—the gap in the continental divide that would take us to the top of Knife Point Glacier. On the rocky slopes near camp we marveled at the tiny haystacks drying in the sun. Hearing panicky peeps and catching fleeting glimpse of gray, we knew that these were the work of pikas. Resembling giant hamsters, but most closely related to hares, these creatures are taxonomic oddities, having been placed in a family that has a single genus. Above our camp, Harrower Glacier clung to the side of the valley and looked reasonably accessible, but there had never been reports of grasshoppers embedded in this ice. Various geological reports from the 1930s made mention of five glaciers in the Wind Rivers as having grasshopper deposits. However, surveys in the 1950s did not report the presence of grasshoppers within these bodies of ice, so their contents had presumably been lost to recession and melting. It seemed that Knife Point Glacier was to be our last great cause for hope.

  When we reached Indian Pass the next morning, Knife Point Glacier lay below us, stretching more than a mile down the windswept valley. The top of the glacier was still covered in a thin crust of snow. Knowing the upper reaches of the glacier were deeply crevassed and that fragile snow bridges may have formed over these gaps, we roped up to descend to where the ice had shed its snowy blanket. Working systematically, Larry and I scoured the upper reaches of the glacier while Charlie and Craig went about their business of collecting water and ice samples and surveying the glacier for comparison to earlier measurements. They had told us that the best places to find insects on their previous trips had been lower on the glacier, but we wanted to carefully inspect as much of the ice as possible. Starting at the top made sense logistically, but not emotionally. The day was a complete bust, except for finding a few scattered moths and wasps that had obviously arrived in recent times.

  The next day we worked our way down to an area where the glacier leveled out, just below an immense rock buttress that emerged from the middle of the ice field. It was easy to imagine this outcropping extending under the ice, creating a dam that caused the glacier to cascade in slow motion over the submerged ridge. Within minutes I heard Larry shout. The glacial ice crunched under my crampons as I hurried from the edge of the moraine, where I’d been jotting notes.

  As I reached him, I dropped to my hands and knees. The surface of the rotting ice was pockmarked with small pits. In the cavity that he’d marked with the tip of his ice ax lay a crumpled form about an inch long, soaked in meltwater. Its legs were missing but the bulbous head, powerful thorax, tapered abdomen, and straight wings left no doubt that this was the body of a grasshopper—or a locust. In the intense sunlight that cuts through the thin air of 12,000 feet, the soggy black remains had warmed faster than the surrounding ice and the body formed a meltwater pool. The area was littered with bodies. Like a Lilliputian version of the Night of the Living Dead, the insect corpses were emerging from their graves.

  Larry’s ruddy face split into a grin. He had indeed found the “mother lode,” as we came to call this section of the glacier. He’d stuck with me through August snowstorms, lung-searing climbs, and horrifically bad advice from local guides. The afternoon passed in quiet exuberance as we gently placed the limp and sodden bodies in numbered vials.

  The exquisite preservation of so many individuals was a direct result of the mechanism by which this and other glaciers trapped insects. Swarms originating on the western slopes of the Rockies were funneled up the mountain valleys by winds and carried over the passes. A few of these valleys, because of their orientation relative to prevailing winds and their proximity to the habitats where the locusts emerged and aggregated, functioned as thoroughfares during the insectan rush hour (actually a matter of a few days or weeks each year). Some of these montane routes had been carved by glaciers and the rivers associated with their runoff, and in a few cases the ice still persisted at the head of the valley. As the locusts were carried upward, the falling temperature chilled a portion of the swarm, which dropped to the ice, where it was soon immobilized by the cold. In some cases, as the air was funneled through the frigid gaps in the mountains, localized downdrafts and other such perturbations would have forced some of the insects onto the ice.

  Based on our findings, the insects must have been interred in huge numbers. We hypothesized that they had been washed by summer meltwater into the crevasses some 300 yards above us. This initial process had not been possible in the glaciers that we had studied in previous years, as these bodies of ice generally lacked the size and topographic variation to form numerous crevasses (except for the third Grasshopper Glacier, and perhaps well-preserved insects will be the reward if and when someone finally accesses the main body of ice). As the ice flowed down the mountain, the crevasses closed and entombed their contents. The frozen creatures were carried over the ice fall formed by the rock outcropping above us and were then brought to the surface by the turbulent flow at the base of the cascade. It was like casting a fishing lure in the still water above a log dam, allowing it to be swept over the waterfall, and then seeing it bob to the surface in the churning water below the cascade.

  Charlie and Craig had determined from their work that the glacier was flowing at about six and a half feet per year. So, if our inferences were correct, it should have taken about 150 years for the bodies to travel the 300 yards from the crevasses to where they were found. Months later, our radiocarbon dating placed the time o
f deposition between 100 and 200 years ago. Given the remarkable sequence of events that ensured both the preservation of the bodies deep within the ice and their return to the surface, perhaps it was not surprising that we’d failed to find well-preserved remains until now.

  The thigh-burning trudge back up the glacier, over the pass, and back down to camp at the end of the day was as grueling as ever, but the pain felt strangely good. That night, as Larry brought water up from the stream and Craig and Charlie fixed a dinner of rehydrated jumbo shrimp on a bed of rice (an absurdly decadent meal that they’d snuck into the food boxes in anticipation of a celebration), I dissected one of the few males that we’d collected. Tearing into the body would destroy the integrity of this rare and valuable specimen, but I had to know what we had found. By the hissing, white light of a Coleman lantern, I teased apart the abdomen. The hardened cingula and epiphallus clung weakly to the soft, decomposing tissues within the shriveled abdomen. These were the surviving structures of the internal genitalia, the feature that Theodore Hubbell had found to be so powerfully informative decades earlier. A field microscope provided enough magnification to eliminate any doubt. We’d found the Rocky Mountain locust.