Question

Why did silkworms have to spun a cocoon ??

Answer 1

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Silkworms are easy, fun and educational to grow in a classroom or at home. They are caterpillars that spin a silk cocoon and change into moths while inside. After hatching from an egg, the worms take one month to grow large enough to spin the silk. They spend three weeks in the cocoon, then emerge as a moth to mate and lay eggs. The eggs hatch into worms in a few weeks, and then the cycle continues.

Silkworms go through four stages of development, as do most insects:  egg, larva, pupa and adult.  The adult (imago) stage is the silkworm moth. The larva is the silkworm caterpillar.  Since the silkworm grows so much, it must shed its skin four times while it is growing.  These stages-within-a-stage are called instars.  The Latin (scientific) name for the silkworm is bombyx mori, which means "silkworm of the black mulberry tree".

Answer 2

Because it is natural and of there menstruation cycle