They came, they ate, they left

April 22, 2005

Did you know that vast swarms of locusts once plagued the northwestern states of the US? Every few years, Rocky Mountain swarms would descend on the farmsteads and wreak havoc of biblical proportions. At the height of the 19th century, swarms are estimated to have totalled about 15 trillion individual insects, or 8.5 million tons of meat on the wing, rivalling the 11 million tons of bison meat on the hoof. Then, by the early 20th century, the plagues stopped and it dawned on people that the Rocky Mountain locust appeared to have become extinct.

While near-extinction of the bison due to over-hunting was obvious for all to see, it almost beggared belief that 15 trillion locusts could disappear with no obvious cause. Is the locust really extinct and if so, what caused its extinction? These questions underlie Jeffrey Lockwood's book. He starts with a pioneering farmer facing a locust swarm then jumps ahead 120 years to his own search of Rocky Mountain glaciers for locusts entombed in ice. Why he should be doing this is not clear until much later in the book.

Eight chapters range over a variety of locust-related topics: the early settlers who like the ancients saw locust plagues as a punishment from God; descriptions of the bizarre machinery and numerous fruitless attempts to control rampaging swarms; discussion and documentation of how the locusts influenced the religious and political lives of affected states; short biographies of the notable entomologists first involved in the locust problem and finally, the disappearance of the pest. We then get to the six chapters containing the nitty-gritty.

"A wolf in sheep's clothing" describes how Sir Boris Uvanov showed that a Caucasian grasshopper species called Locusta danica was one and the same as Locusta migratoria . Clever breeding experiments showed that crowded L. danica produced L. migratoria offspring and vice versa in uncrowded conditions. People applied the conclusion to the Rocky Mountain locust - Locusta spretus -and suggested the closely related Locusta sanguinipes as the non-migratory form. But no one could achieve Uvanov-like results, a problem compounded by the absence of living L. spretus . Controversy raged. Was the Rocky Mountain locust alive and well, biding its time masquerading as L. sanguinipes or was it really extinct? If the former, why had the swarms stopped? Lockwood hoped to test the polymorphic hypothesis by collecting specimens preserved in glaciers and subjecting them to DNA and other biochemical analyses.

This is a fascinating book. Lockwood misses no opportunity to digress, ranging from the suffering that body lice caused pioneer settlers to the private lives and bureaucratic tribulations of trail-blazing entomologists, and from explaining the arcane rules of taxonomic nomenclature and the posthumous glory one can expect by naming a new species to berating journals that rejected certain of his papers as "natural history". The chapters on his glacier expeditions are entertaining. Surprisingly, he considers his riskiest moment in the field a close encounter with a falling boulder rather than his close encounter with a surly wrangler who afterwards shot and killed the expedition's hosts. The meandering style makes the book entertaining but obfuscates the big picture. Even so, most people should find it interesting.

So what are the answers? Lockwood rejects the idea that L. spretus flourishes disguised as L. sanguinipes and proposes an accidental extinction from restricted ecological disturbances at critical times in the population cycle. Read the book to see what probably destroyed this amazing pest species.

Graham Elmes is an honorary research fellow at the Natural Environment Research Council.

Locust: The Devastating Rise and Mysterious Disappearance of the Insect that Shaped the American Frontier

Author - Jeffrey A. Lockwood
Publisher - Basic Books
Pages - 294
Price - £14.99
ISBN - 0 7382 0894 9

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