A silkworm starts its life as a tiny egg laid by the female moth. The egg is just about this size: . The egg, laid in the summer or early Spring, remains dormant until the warmth of spring stimulates it to start developing. When silkworms first hatch in the spring, they are tiny—3 mm or so (about 1/8")—and hairy. They require young tender mulberry leaves during their first few days. As they grow, they can eat tougher leaves, and late in their development they will eat any mulberry leaf you can supply.
The larvae advance through five stages of growth, called instars. The silkworm literally outgrows its skin five times, and moults its outgrown skin. With the first moult the silkworm loses its hairy exterior, and for the rest of its larval life its skin is soft and smooth.
Silkworms grow rapidly, eventually reaching the size of your ring finger. Then they spin beautiful oval white or yellow cocoons in which they pupate. After 2–3 weeks the creamy-white adult moths emerge from the cocoons. They clamber around, vibrate their wings rapidly, and mate, but they don't fly
or attempt to escape from their container. During the adult phase of the life cycle, the silkworm moths do not eat or drink. After mating, the female lays a profusion of eggs, and the moths die.
Males and females look slightly different, and students will be able to tell them apart with a little practice. The female has a larger abdomen. The male has a much larger pair of antennae, which look like long rakes or comb-shaped eyebrows, and vibrates its wings rapidly to attract a female.
Silkworm Feeding Silkworms eat mulberry leaves; lots of them! But getting leaves in late spring and winter months is nearly impossible, as the trees are deciduous.
The silkworm eggs must hatch when mulberry leaves and catkins (flowering portion of the mulberry tree) are available. If you are not sure when mulberry trees begin budding in your area, ask a neighbour or enquire at a nursery. We now also sell Mulberry Silkworm Chow which is another food source for your Silkworms.
Habitat. A shoe box is all that you need to make a silkworm habitat. Choose a place in the room where the silkworms will be warm but not in direct sunlight. Place the shoe box in an open plastic bag, or drape a sheet of plastic over the box. The idea is to reduce evaporation from the leaves a bit without developing a humid environment.
If the eggs are scattered all over the box, that is OK, but the larvae should be placed on a leaf. New larvae must be rounded up each day and delivered to a fresh mulberry leaf.
Larva. Silkworm larva are delicate at first and should not be handled for the first 2 weeks except with a tiny paintbrush. By the time the larvae are 2 cm (1") long, students can carefully pick up and gently hold them. The larvae seem to survive better if they are kept together in a single culture early in life—later they can be kept in pairs or small groups on students' desks.
Plan for spinning. Get a medium-size corrugated cardboard box and a couple of paper egg cartons. Open the egg cartons and attach them to the inside walls of the box. The silkworms will spin in the depressions in the egg cartons. The silkworms must all be in this box for spinning their cocoons. The time for this will be signalled by the first larva that starts to spin, either in your class habitat or, more likely, in one of the group habitats.
Prepare for silkworm moths. Once the larvae spin cocoons, they require no further care. The moths will emerge in a couple of weeks and can be handled by students. They do not eat or drink—they mate, lay eggs, and die.
Prepare for mating and egg laying. Get a large flat box, or cut a taller one down to about 10 cm (4"). Line the bottom with paper. As the adults emerge, move them to this new box. The moths will stay in the open box. The females will lay eggs on the paper, making them easy to collect.
Collect eggs. The eggs will remain viable for a year with minimal care. Seal them in a labelled zip bag and put them in the refrigerator (not the freezer!) as soon as all the moths have died. If you don't refrigerate the eggs, they will still hatch, but over an extended period of time instead of all at once.