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National Geographic : 1970 Apr
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begin five to seven days of pupation, the miracle of metamorphosis that transforms its warty, ta pered body into the graceful dome of the adult. Darkening, it awaits final transformation. went to the High Sierra in early February and marked thousands of aggregating beetles with yellow and blue paint. When they left the moun tains, we estimated the wind direction and drove some thirty miles southwest, toward the valley. With insect nets we swept the vegetation, look ing for marked ladybugs. Considering the vast area involved, it would have been fantastic luck to find even one marked beetle. We were not that lucky. Balloons Fail to Follow Flyways Later, we tried helium-filled weather balloons fitted with thermostats which were preset to valve off either helium or water ballast as the balloons rose above or descended below the 55° zone. Thus we hoped to keep them drifting in the same layer of moving air sought by the wind borne beetles. We planned to follow the 15-foot balloons by airplane and automobile; where they touched down we hoped to find marked beetles. Unfortunately, our three balloons never got beyond the Sierra. Two exploded before reach ing the 55° zone, and the third soared thousands of feet above the zone and burst. Someday I hope to hire a manned helium bal loon, take thermometer, binoculars, and camera aboard, and ride it from the mountains to the 55° level, drifting with the wind in that zone. Then a search in the area where the balloon lands would immensely increase the chances of finding marked beetles. Sometimes, during the beetles' return flights from the mountains, the wind blows them off course or beyond their goals. Ladybugs that winter in the Coast Ranges often finish their return journey far out in the Pacific. Days later, the sea washes up millions of dead beetles reddish ribbons stretching for miles at high water mark along the beaches. The migration ends about sunset, when the 55° zone descends to earth. If the ladybugs land in aphid-free areas, they will take off again in search of prey-filled fields. If they fail to find aphids before exhausting their fat reserves, they are doomed to starvation. The lucky ones end up in fields of alfalfa, bar ley, wheat, and sugar beets-all favorite haunts of aphids. By early May all the adult beetles are dead. But each female has laid, on low-lying vegetation, clusters of from 10 to 50 oval, yel lowish eggs, to launch a new generation. Fecundity of the female convergent depends upon the number of aphids available. One lady bug, arriving in an alfalfa field after its long flight from the mountains, must eat at least 549
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