Silkworm

• The adult can neither fly nor feed: it has no working mouthparts.
• Its only role as an adult is to breed before dying a few days later.
• It has not existed in the wild for thousands of years; it is a wholly domesticated species.
• It is the world's only fully domesticated insect, alongside the honey bee, and unlike the bee it does not survive in the wild.
• Domestication has left it helpless outside the rearing house: the adults do not fly, barely move and do not eat, and the caterpillars no longer grip branches well or escape from predators.
• It was domesticated in China some 5,000 years ago, and the secret of silk was guarded for centuries on pain of death.
• Each cocoon is made of a single continuous thread of fibroin, between 600 and 900 metres long.
• To obtain the silk, the chrysalis must be killed with steam or heat before it emerges, because on breaking out it snaps the thread. Around 2,500 cocoons are needed for one kilo of silk.
• It was one of the first animals to have its genome sequenced for industrial purposes, and today it is used as a biofactory: transgenic lines have been created that produce silk with spider-silk properties, or pharmaceutical proteins.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat and environment

Only in human care (sericulture); it has not existed in the wild for thousands of years

Birth weight

A microscopic egg; the newly hatched larva 2-3 mm long

Size at birth

2 - 3 mm long at hatching

Sexual maturity

The adult butterfly can breed as soon as it emerges from the chrysalis

Gestation / incubation

7-14 days for the egg to hatch; a full cycle from egg to adult of 45-55 days

Litter / clutch size

300 to 500-600 eggs per clutch (~400 in multivoltine strains, 500-600 in univoltine and bivoltine ones)

Sources consulted: Agriculture.Institute · Britannica (Silkworm moth) · ResearchGate (silkworm life cycle diagram) · PMC (Mlx gene domestication study) · PeskyLittleCritters · Britannica, ficha Silkworm moth · ficha de especie de Bombyx mori · Animal Diversity Web, Bombyx mori

Best time: A fully domesticated species that no longer exists in the wild: it depends entirely on human beings and is only seen in silk farms