Christopher Grimes age 9s Menlo Park$ Ca;

Why do insects make cocoons?

Cocoons are made by moths who are, of course, first cousins to the butterflies. Insects of this family go through a sleeping beauty stage on the way to growing up. They doze off as caterpillars and wake up as beautiful moths. The little smarties know how to protect themselves during their sleeping stage, Most of them sleep in a hard shelled crysalises. A few of the moths spin themselves silken cocoon blankets.

Any insect has a hard time growing up. You can grow by adding to your bones ahd flesh. An insect cannot do this. It has no inside bones. Its soft body is encased in a tough coat that refuses to grow or stretch. As the body grows, the insect must molt its old coat and grow a new one.

The cocoon insects do all their growing as caterpillars. Like the silkworm, which is a caterpillar, each hatches from an egg. The tiny fellow starts at once to dine on his favorite salad. The silkworm eats mulberry leaves. And my how he eats.  In a few days he is ready to burst his skin. A larger skin has already grown all tucked under the old one. The old one bursts and the silkworm crawls out and gives his new coat a few hours to stretch to the proper fit.

He then goes right back to his eating. In month he has molted four times, His caterpillar, or larva stage, is no coming to a close. He has eaten enough to last a lifetime and the little fellow feels groggy. He gropes around lifting his front end in search of a twig. He finds one and starts to spin a thread from his tail end. This is a thread of tough silks strong enough to fix his chubby body firmly to the twig.

The silken thread then becomes finer, The little silkworm twists and wriggles as he weaves the silk around himself n figures of eight. He uses about half a mile of silk in a single thread, When the job is done he sleeps in his golden cocoon. All his beauty seems to have gone into his cocoon. For when he wakes up in a couple of weeks the silkworm is a. very ordinary looking moth.

Other cocoon spinners save some of their beauty for the final stage of life. Their grey or brown silton cocoons wait out the winter clinging to bare twigs or lying on the ground. A certain fat cocoon may hatch into a big Polyphemus moth, soft tan with touches of" pink and two blue eye spots on the wings: The spice brush caterpillar wraps his cocoon in a leaf. He hatches into a big brown beauty. A certain fat oval cocoon wakes up to find he has become a glamorous luna moth. All these sleeping beauties weave their own cocoons much as the silkworm weaves his own cocoon of a single thread of soft silk.