Plagues: The Manic Locust

The desert locust (Schistocerca gregaria) is a hairy, six-legged, doublejawed grasshopper whose behavior has been exasperation and puzzling mankind ever since his appearance in Exodus as one of the ten plagues inflicted on Egypt by a wrathful Jehovah. Much of the time he is a normal grasshopper, evenly dispersed and foraging alone. Then suddenly, and at unpredictable intervals, he turns into a mob, blackening the skies like a tornado.

The manic change in his personality is apparently triggered by some violent alteration in his environment, such as sharp fluctuations in temperature or humidity. At such times, he develops a voracious appetite. He and his fellows move relentlessly across countries and continents, consuming almost everything in their path that man, beast or insect could possibly eat. In the wake of a swarm, the fields and the trees are stripped bare—as if some huge vacuum cleaner had passed over the land. One ton of locusts, which is only a small platoon in a typical swarm, can consume as much in a day as ten elephants, 25 camels or 250 people. Over the centuries, the locust’s sporadic depredations have inflicted famine on huge areas of Central Africa and Lower Asia—from Morocco to India, from Tanzania to Turkey.

Satellites and Field Scouts. Nine years ago, the Food and Agriculture Organization of the United Nations launched a program to check locust “plagues.” Weather satellites and air spotters began to track locust concentrations and swarms. A system of field scouts was set up in 42 countries to report locust whereabouts. The Anti-Locust Research Center, established in London in 1921, coordinates this information and forecasts locusts’ flight direction. Local governments dispatch spray planes to meet the hordes or treat breeding areas.

In the common effort, even Israel and the Arab countries have cooperated, and still do. Last week, for the first summer in 40 years, London’s “situation summary” did not list a single menacing locust swarm. The FAO was pleased but not triumphant. Quite likely, as the FAO was the first to point out, an atypical lack of rainfall had inhibited breeding, since the locust’s eggs must absorb their weight in water to hatch. Thus the FAO cautioned against concluding that the locust had simply dropped out of the picture. “He is still a global menace in a trough of inactivity,” said Paul G. Hoffman, the U.N.’s development program administrator.

Making Contact. Even so, the FAO feels that its program is succeeding. In 1958, locusts devoured 167,000 tons of crops in Ethiopia, starving thousands. Last summer the anti-locust London Center got reports of gathering clouds of locusts that posed an even greater threat. From weather satellite pictures of cloud formations, trackers could map wind patterns. Since locusts ride the winds, spray planes knew where to go. Once they had made contact, they dumped their loads of spray through atomizers, one right after the other, until the swarms were stopped. On the ground, pesticide squads struck breeding areas. The winged locusts were turned back, and the young locusts died before they could develop wings. The FAQ thus managed to reduce a possible plague to a minor annoyance.