With little stones or bits of leaves The larva of the caddis fly With silken strands together weaves A house, secure from prying eye, Pretending he's a stick or stone When hungry beetles wander by.
DID you ever look down into a pond and see a bundle of sticks moving about? This portable "log cabin" is the house or case of a small, worm-like animal, called a "caddis worm," or caddis fly larva.
The sticks which make up the material of the caddis worm's house are glued together with strands of "silk." This silk comes out of an opening in the lower lip of the animal. At first it is soft and sticky, like glue, but it soon hardens. The inside of the
caddis worm's house is smooth, because it is lined with this silk.
The caddis worm has a pair of tiny hooks at the end of his body. With these he fastens himself firmly inside his case. While he is inside his house, the larva is fairly safe. But if he is hungry, or wants to move about, he must put out his head and his three pairs of legs. When an enemy comes near, the larva quickly disappears into his case.
The middle part of his body, to which his legs are attached, is called his thorax. All these parts, heads, legs, and thorax, are covered by an exoskeleton.
The third division of the caddis worm's body, behind his last pair of legs, is called his abdomen. Along the sides of this abdomen you will usually find gills, which look like white threads. Oxygen from the water passes through the walls of these gills and is carried through the body of the animal in many fine, branched airtubes. You will remember that oxygen is carried through
the body of the crayfish by his colorless blood.
The caddis worm's body is divided into head, thorax, and abdomen. It has three pairs of jointed legs attached to the thorax. It has an exoskeleton. Oxygen is carried through the body in many fine, branched airtubes, or tracheae, instead of in the blood. Because of these facts you will know that the caddis fly larva, in spite of his common name of caddis worm, is not a worm at all, but an insect.
The caddis worm is usually hungry. Tiny plants or animals are his food. Some of these are too small for us to see without a microscope, but there are many of them living in the water. Some caddis worms eat their neighbors-even other caddis worms.