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National Geographic : 1969 Aug
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eggs, and fresh bush vegetation for the off spring, the locust population exploded." The confirmation was spread before us on maps that reached from ceiling to floor. Clus ters of red, green, and black tabs in different shapes marked every known locust sighting - triangles for swarms, squares for smaller groups, and circles for marching infants. Starting at the Red Sea, some clusters ran inland along the southern edge of the Sahara to Africa's west coast; others stretched across the Arabian Peninsula and the Persian Gulf into Iran, Pakistan, and India. By plotting those swarm sightings at every Secret of the locusts WHERE DO THEY ALL come from? The centuries question posed by a locust swarm was answerec 1921 by Sir Boris Uvarov (right). He discovered that of the familiar green grasshoppers of the African c Asian bush is really the ravenous locust in another gu When repeated rains dampen the desert sands, thousal of eggs hatch. The hoppers constantly touch one anoti triggering a change of behavior and color; they seek e, other's company and turn yellow, black, and red. In the Anti-Locust Research Centre in London, foui ed by Sir Boris, an experiment offers proof. A fan kei tiny threads swirling inside a jar (left). As the thre; brush a grasshopper, simulating the touch of its kin slowly changes color. A laboratory encounter (below) between examples the two guises shows the differences in coloring. Boris, knighted in 1961 for his research, is complete volume two of his monumental GrasshoppersandLocu point they occur, the London scientists de velop a pattern of locust movement that no single country in the threatened area can see. From that pattern, they draw up forecasts of probable flight directions and dispatch inva sion alerts if necessary. "We watch wind directions particularly," Dr. Peter Haskell, the British center's director, explained. "Locusts have no maps, no homing instinct, nor much control over where they go. About all they can do is hitch a ride on the passing winds and hope for the best. "That's why it is difficult to tell how much damage they may do. The wind can carry 209
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