THE PROCESSIONARIES
There is an old story about a Ram which was thrown into the water from on board ship, whereupon all the sheep leaped into the sea one after the other; “for,” says the teller of the story, “it is the nature of the sheep always to follow the first, wheresoever it goes; which makes Aristotle mark them for the most silly and foolish animals in the world.”
The Pine Caterpillars are even more sheeplike than sheep. Where the first goes all the others go, in a regular string, with not an empty space between them.
They proceed in single file, each touching with its head the rear of the one in front of it. No matter how the one in front twists and turns, the whole procession does the same. Another odd thing: they are all, you might say, tight-rope walkers; they all follow a silken rail. The leading Caterpillar dribbles his thread on the path he makes, the second Caterpillar steps on it and doubles it with his thread; and all the others add their rope, so that after the procession has passed, there is left a narrow white ribbon whose dazzling whiteness shimmers in the sun. This is a sumptuous manner of road-making: we sprinkle our roads with broken stones and level them by the pressure of a heavy steam-roller; they lay over their paths a soft satin rail!
“They Proceed in Single File.”
What is the use of all this luxury? Could they not, like other Caterpillars, walk about without these costly preparations? I see two reasons. It is night when the Processionaries go forth to feed, and they follow a very winding route. They go down one branch, up another, from the needle to the twig, from the twig to the branch, and so on. When it is time to go home, they would have hard work to find their way if it were not for the silken thread they leave behind them. It reminds one of the story of Theseus (in the “Tanglewood Tales,” or the old mythologies), who would have been lost in the Cretan labyrinth if it had not been for the clue of thread which Ariadne gave him.
Sometimes, too, they take longer expeditions by day, marching in procession for thirty yards or so. They are not looking for food; they are off on a trip, seeing the world, perhaps looking for a place to bury themselves later on, in the second stage before they become Moths. In a walk of this distance, the guiding-thread is very necessary.
The guiding-thread, too, brings them all back home to the nest when they are separated, hunting for food in the pine-tree. They pick up their threads, and come hurrying from a host of twigs, from here, from there, from above, from below, back to the group. So the silk is more than a road: it is a social bond that keeps all the members of the community united.
At the head of every procession, long or short, goes the first Caterpillar, the leader. He is leader only by chance; everything depends upon the order in which they happen to line up. If the file should break up, for some reason, and form again, some other Caterpillar might have first rank. But the leader’s temporary duties give him airs of his own. While the others follow passively in a close file, he, the captain, tosses himself about and flings the front of his body hither and thither. As he marches ahead he seems to be seeking his way. Does he really explore the country? Does he choose the best places? Or are his hesitations only the result of the absence of the guiding-thread the rest follow? Why cannot I read what passes under his black, shiny skull, so like a drop of tar? To judge by actions, he has sense enough to recognize very rough places, over-slippery surfaces, dusty places, and, above all, the threads left by other Caterpillars. This is all, or nearly all, that my long acquaintance with the Processionaries has taught me about their brain power.
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.”
That they should remain up there, hard pressed by hunger and the lack of shelter, when nothing prevented them from going away, seemed to me unthinkable foolishness. Facts, however, forced me to accept the incredible.
The Caterpillars keep on marching round the vase for hours and hours. As evening comes on, there are more or less lengthy halts; they go more slowly at times, especially as it grows colder. At ten o’clock in the evening the walk is little more than a lazy swaying of the body. Grazing-time comes, when the other Caterpillars come crowding out from their nests to feast on the pine-needles. The ones on the vase would gladly take part in the feast; they must have an appetite after a ten hours’ walk. A branch of pine is not a hand’s breadth away from them. To reach it they have only to go down the vase; and the poor wretches, foolish slaves of their ribbon that they are, cannot make up their minds to do so. At half-past ten I leave them to go to bed; I am sure that during the night they will come to their senses. At dawn I visit them again. They are lined up as on the day before, but motionless. When the air grows a little warmer, they shake off their torpor, revive, and start walking again in their circle.
Things go on as before during the next day. The following night is very cold. The poor Caterpillars spend a bad night. I find them clustered in two heaps on the top of the vase, without any attempt at order. They have huddled together to keep warm. Perhaps, now that they are divided into two parts, one of the leaders, not being obliged to follow a Caterpillar in front of him, will have the sense to break away. I am delighted to see them lining up by degrees into two distinct files, with two leaders, free to go where they please. At the sight of their large black heads swaying anxiously from side to side, I am inclined to think they will leave the enchanted circle. But I am soon undeceived. As the ranks fill out, the two sections of the chain meet and the circle is formed again. Again the Caterpillars march round and round all day.
The next night is again cold, and the Caterpillars gather in a heap which overflows both sides of the fatal ribbon. Next morning, when they awake, some of them who find themselves outside the track actually follow a leader who climbs to the top of the vase and down the inside. There are seven of these daring ones. The rest pay no attention to them and walk round the circle again.
The Caterpillars inside the vase find no food there, and retrace their steps along their thread to the top, strike the procession again, and slip back into the ranks.
Another day passes, and another. The sixth day is warm, and for the first time I see daring leaders, who, drunk with heat, stand on their hind-legs at the extreme edge of the vase and fling themselves forward into space. At last one of them decided to take the plunge. He slips under the ledge and four follow him. They go halfway down the vase, then their courage fails and they climb up again and rejoin the procession. But a start has been made and a new track laid. Two days later, on the eighth day of the experiment, the Caterpillars—now singly, then in small groups, then again in strings of some length—come down from the ledge by starting on this fresh path. At sunset the last of the Caterpillars is back in the nest at the foot.
I figure that they have walked for eighty-four hours, and covered a good deal more than a quarter of a mile while traveling in the circle. It was only the disorder due to the cold nights that ever set them off the track and back to safety. Poor, stupid Caterpillars! People are fond of saying that animals can reason, but there are no beginnings of a reasoning power to be seen in them.
