Silkworms are actually a caterpillar. They are the larvae of the Silkworm Moth Bombyx mori and only one stage of the moth life-cycle.
Silkworms spin their silk from two glands in their mouth area. One gland produces the silk fibre; the other produces a sticky saliva called seracin which holds the cocoon together and gives it it’s rigidity.
The larval stage is the only eating phase in the life cycle of the silkworm moth and they make the most of it!
During this phase, the larvae eat voraciously. They eat only fresh leaves of the mulberry tree. As they eat, they grow rapidly and every few days must shed their skin to allow continued growth and development. This is called a “moult”.
Over the course of the larval stage, the silkworm will moult four times. The first is around four days after hatching, then every 4-7 days after that. The period between moults is called an “instar”.
When moulting, the worm stops eating and attaches its rear end to a leaf with a thin strand of silk.
It sits up in “prayer position” then walks forward as it attempts to wriggle out of its old skin.