The particular species of Caddis-worm I have chosen is found in muddy-bottomed, stagnant pools crammed with small reeds. It is the little grub that carries through the still waters a bundle of tiny fragments fallen from the reeds. Its sheath, a traveling house, is an elaborate piece of work, made of many different materials.
The young worms, the beginners, start with a sort of deep basket in wicker-work, made of small, stiff roots, long steeped and peeled under water. The grub that has made a find of these fibers saws them with its jaws and cuts them into little straight sticks, which it fixes one by one to the edge of its basket, always crosswise. This pile of spikes is a fine protection, but hard to steer through the tangle of water-plants. Sooner or later the worm forsakes it, and builds with round bits of wood, browned by the water, often as wide as a thick straw and a finger’s breadth long, more or less—taking them as chance supplies them.
It does not always use wood, however. If there are plenty of small, dead Pond-snails in the pond, all of the same size, the Caddis-worm makes a splendid patchwork scabbard; with a cluster of slender roots, reduced by rotting to their stiff, straight, woody axis, it manufactures pretty specimens of wicker-work like baskets. With grains of rice, which I gave the grubs in my glass pond as an experiment, they built themselves magnificent towers of ivory. Next to the sheaths of snail-shells, this was the prettiest thing I ever saw the Caddis-worms make.
THE PIRATES’ ATTACK
What is the use of these houses which the Caddis-worms carry about with them? I catch a glimpse of the reason for making them. My glass pond was at first occupied by a dozen Water-beetles, whose diving performances are so curious to watch. One day, meaning no harm and for want of a better place to put them, I fling among them a couple of handfuls of Caddis-worms. Blunderer that I am, what have I done! The pirate Water-beetles, hiding in the rugged corners of the rockwork, at once perceive the windfall. They rise to the surface with great strokes of their oars; they hasten and fling themselves upon the crowd of carpenter Caddis-worms. Each Beetle grabs a sheath by the middle and tries to rip it open by tearing off shells and sticks. While this is going on, the Caddis-worm, close-pressed, appears at the mouth of the sheath, slips out, and quickly escapes under the eyes of the Water-beetle, who appears to notice nothing.
The brutal ripper of sheaths does not see the little worm, like a white sausage, that slips between his legs, passes under his fangs, and madly flees. He continues to tear away the outer case and to tug at the silken lining. When the breach is made, he is quite crestfallen at not finding what he expected.
Poor fool! Your victim went out under your nose and you never saw it. The worm has sunk to the bottom and taken refuge in the mysteries of the rockwork. If things were happening in a larger, outdoor pond, it is clear that, with their clever way of removing themselves, most of the worms would escape scot-free. Fleeing to a distance and recovering from the sharp alarm, they would build themselves a new scabbard, and all would be over until the next attack, which would be foiled all over again by the very same trick!