_The duel began just after sunrise on Wednesday, at 150 miles per hour, 50 feet above the ground. Below: billions of voracious, recently hatched migratory grasshoppers, Melanoplus sanguinipes, shock troops of the worst insect infestation here in at least 25 years. Able to fly hundreds of miles, the inchlong insects devastated the land in the 1930s during the Dust Bowl. Above: Tony Martinez of Great Bend, Kan., agricultural aviator, armed with a thermos of strong coffee and a 400-gallon tank of insecticide, the advance guard of perhaps the largest armada of crop dusters ever assembled on the high plains. "Spray on," Mr. Martinez said over his radio, releasing the hand lever on his plane's insecticide reservoir. Stacy Timmons, of Lubbock, Tex., flying not far from Mr. Martinez's wingtip, chimed in: "I think I saw a grasshopper back there, but he's already starting to be fixed."