A Plague of Locusts

(This 696th column was first published in the August 1, 2004 issue of The Buffalo Sunday News.)

Despite this wet summer cicadas have been singing in our backyard for several weeks now. Because there are not too many, I consider them benign and even find their strident buzzing quite pleasing. These insects are often called locusts and this year's outbreaks in other parts of the country of the 17-year cicada, often misnamed the 17-year locust, reinforces that error.

Although they look somewhat like cicadas, what most entomologists call locusts are in an entirely different insect order. They belong with the grasshoppers. In fact at least one major entomological text no longer uses the name locust, instead calling them grasshoppers as well.

Whatever they were called, one species, the Rocky-Mountain locust was surely the greatest insect scourge of the North American continent. From 1874-1877 and during many earlier periods this single insect species devastated the plains of Kansas, Missouri, Minnesota, Iowa, the Dakotas, Colorado, Wyoming and Montana.

Brief extracts from contemporary accounts will suggest the nature of the locust plague: "They came like a driving snow in winter, filling the air, covering the earth, the buildings, the shocks of grain and everything." "Their alighting sounded like a continuous hailstorm. The noise was like suppressed distant thunder or a train in motion." "They were four to six inches deep on the ground and continued to alight for hours. Their weight broke off large tree limbs." "By dark there wasn't a stalk of field corn over a foot high. Onions were eaten down to the very roots. They gnawed the handles of farm tools and the harness on horses or hanging in the barn, the bark of trees, clothing and curtains of homes and dead animals -- including dead locusts."

God-fearing people recalled Biblical plagues: "The land is as the garden of Eden before them, And behind them, a desolate wilderness."

Scientists described a locust swarm as "living fire", estimated their peak numbers at 15 trillion, their total mass as nearly equivalent to that of the 30-60 million bison that had inhabited the west, and the depredations of a single swarm at two tons of vegetation per hour. Some entomologists also believe that they were at one time the most common animal of their size or greater ever to inhabit the earth.

After the devastation settlers living on a half million square miles of the west (about twice the area of Texas) faced starvation. This catastrophe forced state and federal governments to provide not only food and clothing but even wheat and vegetable seed to replace the supplies for new crops that the starving farmers had been forced to consume. Despite the usual policy failures, some episodes of graft and one recommendation that the pioneers avoid starvation simply by eating the locusts, the better responses set directions for government agricultural policies that continue today.

Plagues those certainly were, but they were not to continue. Outbreaks of other grasshopper species still pose lesser problems for western farmers; however, by the early twentieth century the Rocky Mountain locust was extinct. The last pair, collected on July 19, 1902, is now part of the Smithsonian Institution collection.

From 15 trillion to zero in just 25 years is a remarkable reduction. What caused it has been an open question over the subsequent century.

Now it appears that we have closure on this subject and the scientist who has contributed most to the solution, Jeffrey Lockwood, has written "Locust: The Devastating Rise and Mysterious Disappearance of the Insect that Shaped the American Frontier" (Basic Books). If you enjoy scientific detection, this is a book for you.

I won't give away Lockwood's answer but will record what a Russian discovered early in the 20th century. Most insect species go through a process of change called metamorphosis -- caterpillars change to butterflies, for example -- but Boris Uvarov found that certain grasshoppers also have what he designated different phases. In one phase they are solitary and localized insects; in another they are gregarious, ready to swarm and migrate. The phases of some locusts appeared so different that several were first misidentified as different insects.

In their solitary phase Rocky Mountain locusts were not only less numerous but also far more restricted in range. With their numbers down to the low millions during those periods they were to be found only in the high mountain meadows of Colorado, Wyoming and Montana.

Various hypotheses were offered why they went the rest of the way to extinction -- for example, that somehow their lives were tied to those of the buffalo -- but I find Lockwood's most compelling.

Many of us are saddened by the extinction of passenger pigeons, ivory-billed woodpeckers, great auks and dodos. We may have mixed feelings about losing saber-toothed tigers, woolly mammoths and giant sloths. But surely we should be happy to accept the departure of the Rocky Mountain locust.-- Gerry Rising