[A] (1) Dr. Calcagno said the likeliest explanation for the behavior is the selection pressure of harvesting ― over generations, those caterpillars that did not descend, or did not go far enough, did not survive. (2) O. scapulalis does not exhibit this descending behavior, called geotaxis. (3) “There could be other reasons that explain the tendency to move down, but we have no evidence of what those reasons could be,” he said. (4) This harvesting-induced selection, he added, could be widespread in other pests. (5) Through field and laboratory tests, the researchers discovered that before it stops eating and spins its cocoon, the corn borer travels down the stalk, usually reaching a height at which it is safe.