Most silk used commercially is retrieved from the cocoons of larvae from the mulberry silkworm. While it's theoretically possible to retrieve the cocoons, and the silk thread, after the larvae mature and break out of the cocoon, this is rarely done. If the larvae breaks out of the cocoon, the damage caused results in shorter threads which can only be used in cheaper, less fine silk textiles. Instead, cultivators kill the larvae allowing a controlled separation of the cocoon, and more valuable, luxurious feeling silk.
The light that burns twice as bright, burns half as long.