Solution:The silkworm produces the silk of commercial importance in pupa stage of its life cycle. The egg is the first stage of the silkworm's life cycle. The larva is the vegetative stage where growth takes place.
In pupa stage, as the silkworm prepares to pupate, it spins a protection cocoon. About the size and color of a cotton ball, the cocoon is constructed from one continuous strand of silk perhaps 1.5 km long.
The silk cocoon serves as protection for the pupa. Imago is the adult stage which completes the life cycle of a silkworm.