Silkworm

The silkworm, Bombyx mori, is the larva of the domestic silk moth, a species that no longer exists in the wild and survives only through human cultivation. It was domesticated in China thousands of years ago from a wild ancestor believed to be related to Bombyx mandarina, and has been selectively bred ever since for silk production.

Silkworms feed almost exclusively on mulberry leaves and are raised indoors in controlled conditions on trays or racks. Generations of domestication have left the species unable to fly as an adult and largely dependent on human care for feeding and protection throughout its life cycle.

Beyond their historical and continuing role in silk production, silkworms are widely used in biology classrooms and research as an accessible model for studying insect development and metamorphosis.

• Body is soft, plump, and pale cream to white, with a segmented, cylindrical shape typical of moth caterpillars
• Reaches about 7-8 cm (roughly 3 in) in length at full growth
• Has a small pair of dark, simple eye-like spots near the head and a short, fleshy horn near the rear, typical of silk moth caterpillars
• Moves slowly and is entirely dependent on being placed near a food source, unlike wild caterpillars
• Distinguished from wild caterpillars by its uniformly pale color and lack of the defensive hairs, spines, or camouflage patterns found in most wild species

Silkworms exist only in captivity, reared indoors on mulberry leaves (or a prepared artificial diet) in dedicated silk-farming operations, research facilities, and classrooms around the world, particularly in parts of Asia with a long history of sericulture.

Larvae feed continuously on mulberry leaves, molting through several instars as they grow. In the final instar, a mature silkworm stops feeding and spins a cocoon from a single continuous silk thread that can extend hundreds of meters, produced from a pair of modified salivary glands. As a domesticated species with no independent wild population, the silkworm plays essentially no role in wild ecosystems, but its cultivation supports the textile industry.

Eggs are laid by the flightless adult moth and hatch into tiny larvae that feed on mulberry leaves. Over roughly four to six weeks, the larva passes through five instars, growing substantially with each molt. At maturity, it spins a silk cocoon around itself and pupates inside. In commercial silk production, most cocoons are processed before the adult would otherwise emerge; when allowed to complete development, the adult moth emerges, mates, lays eggs, and dies within days, as domesticated adults do not feed and cannot fly.