Locust: The Devastating Rise and Mysterious Disappearance of the Insect that Shaped the American Frontier. Jeffery A. Lockwood. Basic Books, New York, 2004. 304 pages, illus. $25.00 (ISBN 0558964312 cloth).
The Rocky Mountain grasshopper, or locust, was a migratory insect that in peak population years spread over the Great Plains from Canada to Texas and periodically devastated the crops of homesteaders and farmers. The mystery began late in the 19th century: Instead of another invasion during the next drought cycle, the locust completely disappeared over the course of a few years, without any apparent cause.
Jeffery Lockwood, professor of natural sciences and humanities at the University of Wyoming, set out to reinvestigate the intriguing disappearance of the Rocky Mountain locust, which he calls “the quintessential ecological mystery of the North American Continent,” when existing extinction theories proved untenable. This popular account of his quest to solve this cold-case mystery is a synthesis of his and his students' research over several years.
The Rocky Mountain locust was once the most abundant insect on the Great Plains. In years of peak populations, Lockwood calculates, its numbers rivaled bison populations in both biomass and consumption of forage. Before the plains were settled, periodic swarms of migrating locusts were part of the natural rhythm of the grasslands, particularly during years of drought. That situation had changed by the mid-1870s, however, when farmers and ranchers occupied much of the Great Plains. A drought of several years' duration triggered a massive outbreak of locusts that swept over an immense area, destroying much of the agricultural production and bringing famine to many settlers.
The author recounts several vivid eyewitness accounts of the locust invasion and its aftermath: The swarms of countless flying insects looked like dark storm clouds, and they glittered like snowflakes as they descended out of the sky. They arrived in waves from the more northern regions of the plains during July and August, devouring crops in their path and laying eggs in the soil. The farmers tried desperately to save their crops and to drive the locusts off, but with little success because of the huge numbers of insects. Many families had to abandon their homesteads, and thousands more were threatened by famine, with virtually no food left for themselves or their livestock.
Lockwood's account encompasses the homestead era and the politics of early disaster relief efforts by private, state, and federal agencies. Some limited aid came from frontier Army supplies and other sources, but not enough to avert catastrophe: Settlement of the plains was threatened, and the Rocky Mountain locust was thought to be the greatest obstacle to farming this region.
To deal with this emergency, three prominent entomologists—Charles Valentine Riley, Cyrus Thomas, and Alpheus Packard—were named by the federal government to the newly formed Entomological Commission. They were charged to gather all available information on the locust and to find practical methods for its control. (Lockwood's biographical account of Riley, the brilliant but eccentric head of the commission and later the chief entomologist in the US Department of Agriculture, is particularly entertaining. Riley went on to become the nation's foremost economic entomologist and pioneered the introduction of biological agents for control of introduced pests.) The commission did indeed gather a remarkable amount of detailed information on the ecology, behavior, anatomy, reproduction, and distribution of the locust, and suggested practical ways for the farmers to battle the insects.
Then in the late 1870s, about the time the commission was publishing its work, a wetter climatic cycle brought about a decrease in locust invasions. The locust depradations were expected to rebound in the next drought cycle, but much to the surprise of entomologists, the species disappeared completely. The Rocky Mountain locust is now considered to be extinct.
Several theories to explain the extinction—and one positing that the locust was still alive, masquerading as an extreme migratory form of a common related grasshopper—were put forward over the years, but most have been refuted by Lockwood and other grasshopper specialists through new research and analysis of data. One of the most interesting of these theories was that the ecology of the locust was somehow linked to the great herds of bison, and that the extermination of the latter from most of its range brought about the extinction of the former. These two major and competing grazers had coexisted on the plains for thousands of years, so the idea was advanced that the bison somehow altered the ecology of the grasslands to favor reproduction and survival of the locust. Another theory was that the planting of alfalfa throughout the locust's breeding area in the latter part of the 19th century could have played a role in the insect's extinction; alfalfa, which is palatable to grasshoppers, was shown in laboratory studies to be deleterious to the growth of the insect's immature stages. That the Rocky Mountain locust was a distinct species, and not a migratory form of an extant species, was proved by taxonomic studies on male genitalia and more recently by DNA analysis of specimens recovered from glaciers by Lockwood and his colleagues.
On the basis of a synthesis of the detailed information gathered by the Entomological Commission, settlement records, and other evidence, Lockwood has arrived at a new explanation of the locust's disappearance, which he calls “my habitat destruction theory.” He maintains that cattle grazing and homesteaders' cultivation of a restricted region of the plains—the permanent breeding grounds of the insect—during a population recession of the locust in the 1880s may have irreversibly disrupted locust reproduction. Others had shown that grasshopper eggs fail to hatch if the soil they are deposited in is disturbed by plowing or by other means.
The book is replete with odd facts and interesting characters involved in the locust story. (Among them was the Canadian entomologist Norman Criddle, who collected the last live specimens of the Rocky Mountain locust in 1902. He also invented a grasshopper poison bait known as Criddle's Mixture, composed of horse manure, arsenic, and molasses, that was state of the art in grasshopper control in the early days.) Lockwood works into the book a wide range of information, including the biology of grasshoppers and locusts, the history and politics of the homestead era, and his and his colleagues' expeditions to remote glaciers in the Rocky Mountains to collect rare specimens of the extinct locust, which had been preserved in ice.
Moreover, this tale of a unique case of extinction of an insect pest that threatened settlement of the Great Plains is written in an entertaining and often humorous style. It should be of wide interest not only to biologists but also to Western historians and the general reading public.