The slow march kept on. The rear of the procession of caterpillars emerged from the cloud-bank, and Burl saw that a shining white line was left behind them. No less than eighty great caterpillars clad in white and dingy red were solemnly moving down the mountainside, leaving a path of shining silk behind them. Head to tail, in single file, they had no eyes or ears for anything but their procession. The leader reached the plateau, and turned. He came to the cluster of giant cabbages, and ignored them. He came to a thicket of mushrooms, and passed through it, followed by his devoted band. Then he came to an open space where the earth was soft and sandy, where sandstone had weathered and made a great heap of easily moved earth. The leading caterpillar halted, and began to burrow experimentally in the ground. The result pleased him, and some signal seemed to pass along the eight-hundred-foot line of creatures. The leader began to dig with feet and jaws, working furiously to cover himself completely with the soft earth. Those immediately behind him abandoned their formation, and pressed forward in haste. Those still farther back moved more hurriedly. All, when they reached the spot selected by the leader, abandoned any attempt to keep to their line, and hastened to find an unoccupied spot in the open space in which to bury themselves. For perhaps half an hour the clearing was the scene of intense activity, incredible activity. Huge, ten-foot bodies burrowed desperately in the whitish earth, digging frantically to cover themselves. After the half-hour, however, the last of the caterpillars had vanished. Only an occasional movement of the earth from the struggle of a buried creature to bury itself still deeper, and the freshly turned surface showed that beneath the clearing on the plateau eighty great slugs were preparing themselves for the sleep of metamorphosis. The piled-up earth and the broad, white band of silk, leading back up the hillside until it became lost in the clouds, alone remained to tell of the visitation. The tribesmen had watched in amazement. They had never seen these creatures before, but they knew, of course, why they had entombed themselves. Had they known what the scientists of thirty thousand years before had written in weighty and dull books, they would have deduced from the appearance of the processionary caterpillars--or pine-caterpillars--that somewhere above the banks of clouds there were growing trees and sunlight, that a moon shone down, and stars twinkled from the blue vault of a cloudless sky. But the tribesmen did not know. They only knew that there, beneath the soft earth, was a mighty store of food for them when they cared to dig for it, that their provisions for many months were secure, and that Burl, their leader, was a great and mighty man for having led them to this land of safety and plenty.