The Animal That Cannot Exist Without Us
Bombyx mori, the mulberry silkworm, is the only fully domesticated insect in the world outside the honeybee. It is blind. It cannot fly. Its wild ancestor, Bombyx mandarina, still exists in China and Japan, but Bombyx mori cannot survive outside human care, five thousand years of selective breeding have made it entirely dependent on the people who rear it. A single cocoon contains a continuous silk thread between 600 and 900 metres long, spun from two salivary glands that merge at the moth's spinneret into a single filament coated in a protein called sericin. The thread is not woven. It is secreted, in one unbroken line, over three to four days.
