Silk is obtained from the cocoon spun by the pupal stage of the silk moth (Bombyx mori). The last-instar larva (silkworm) secretes liquid silk from its silk glands and spins a continuous silk thread around itself, forming the cocoon before pupation. The cocoon is then harvested, the pupa is killed by steam or heat, and the continuous silk filament (~300–900 m long) is carefully unwound (reeled). One cocoon provides a single continuous silk filament.