The processions vary greatly in length. The finest one I ever saw was twelve or thirteen yards long and numbered about three hundred Caterpillars, drawn up with absolute precision in a wavy line. If there were only two in a row, however, the order would still be perfect: the second touches and follows the first.
I make up my mind to play a trick upon the Caterpillars which have hatched out in my greenhouse. I wish to arrange their silken track so that it will join on to itself and form an endless circuit, with no branch tracks leading from it. Will the Processionaries then go round and round upon a road that never comes to an end?
Chance makes it easy for me to arrange something of this sort. On the shelf in my greenhouse in which the nests are planted stand some big palm vases measuring nearly a yard and a half in circumference at the top. The Caterpillars often scale the sides and climb up to the molding which forms a cornice or ledge around the opening. This place suits them for their processions. It provides me with a circular track all ready-made.
One day I discover a numerous troop making their way up and gradually reaching the favorite ledge. Slowly, in single file, the Caterpillars climb the great vase, mount the ledge, and advance in regular procession, while others are constantly arriving and continuing the series. I wait for the string to close up, that is to say, for the leader, who is following the circular track, to return to the point from which he started. This happens in a quarter of an hour. I now have a circle of Caterpillars around the top of the vase.
The next thing is to get rid of the rest of the Caterpillars who are on their way up and who might disturb the experiment; we must also do away with all the silken paths that lead from the top of the vase to the ground. With a thick hair-pencil I sweep away the Caterpillars; with a big brush I carefully rub down the vase and get rid of every thread which the Caterpillars have laid on the march. When these preparations are finished, a curious sight awaits us.
The Caterpillars are going round and round on the ledge at the top of the vase. They no longer have a leader, because the circle is continuous; but they do not know this, and each follows the one in front of him, who he thinks is the leader.
The rail of silk has grown into a narrow ribbon, which the Caterpillars keep adding to. It has no branches anywhere. Will they walk endlessly round and round until their strength gives out entirely?
Old-fashioned scholars were fond of quoting the tale of the Donkey who, when placed between two bundles of hay, starved to death because he was unable to decide in favor of either. They slandered the worthy animal. The Donkey, who is no more foolish than any one else, would feast off both bundles. Will my Caterpillars show a little of his common-sense? Will they make up their minds to leave their closed circuit, to swerve to this side or that? I thought that they would, and I was wrong. I said to myself:
“The procession will go on turning for some time, for an hour, two hours perhaps; then the Caterpillars will perceive their mistake. They will abandon the deceptive road and make their descent somewhere or other.”