Coming slowly down the slanting earth was a long, narrow file of living animals. For a time the file seemed to be but one creature, but Burl's keen eyes soon saw that there were many. They were caterpillars, each one perhaps ten feet long, each with a tiny black head armed with sharp jaws, and with dull-red fur upon their backs. The rear of the procession was lost in the mist of the low-hanging cloud-banks that covered the mountainside some two thousand feet above the plateau, but the foremost was no more than three hundred yards away.
Slowly and solemnly the procession came on, the black head of the second touching the rear of the first, and the head of the third touching the rear of the second. In faultless alignment, without intervals, they moved steadily down the slanting side of the mountain.
Save the first, they seemed absorbed in maintaining their perfect formation, but the leader constantly rose upon his hinder half and waved the fore part of his body in the air, first to the right and then to the left, as if searching out the path he would follow.
The tribefolk watched in amazement mingled with terror. Only Burl was calm. He had never seen a slug that meant danger to man, and he reasoned that these were at any rate moving slowly so that they could be distanced by the fleeter-footed human beings, but he also meant to be cautious.
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.