Two Living Displays in the Zoo's Silk Room

Notes from the Silk Room

The zoo's silk room has two nearby displays: young mulberry plants and trays of silkworms. Silkworms are the caterpillar stage of a kind of moth. They eat mulberry leaves. Keeper Elena records changes in both displays. Visitors watch the living things and examine enlarged models of their inside parts. They do not open or injure living plants or animals.

At the plant display, roots spread through the soil. A plant sways when brushed, but its roots remain held in the soil. Water enters through roots and travels upward through tiny tubes inside the stem to the leaves. In daylight, leaf tissue uses light to make food. Bark covers the woody stem. A scrape on an old branch has exposed softer tissue beneath the bark. Elena also keeps a record from a mature mulberry tree. Flowers appeared first, followed by fruits containing seeds. A model shows a small young plant, called an embryo, inside a seed coat. During sprouting, the coat splits and the young root grows out.

At the silkworm display, a caterpillar grips a twig with its legs while moving toward a leaf. Its jaws cut off pieces of the leaf. The pieces enter a gut inside its body. Food is broken down there, and usable food passes into the body. As a caterpillar grows, its outer skin becomes too tight. It sheds that skin and continues growing with a larger covering. A model also shows silk-making glands inside the caterpillar. Material from these glands passes through a small opening on the outside of its head and becomes silk thread.

Before changing into a pupa, a silkworm lays silk thread around itself to build a cocoon. In the zoo's recordings, loose fibers brush against the cocoon while the pupa remains enclosed. Later, an adult moth emerges. The adult is a different stage of the same animal. Eggs develop in reproductive organs inside an adult female moth. After mating, she lays the eggs outside her body. Elena photographs tiny caterpillars hatching from the eggs. Her records also show young mulberry plants sprouting from seeds. The new caterpillars and plants begin growing, while the parent moths and tree remain separate living things.