The Wandering Stage: What It Means When a Silkworm Stops Eating

The Most Misread Behaviour in the Cup

A silkworm that suddenly stops eating and begins moving restlessly around its container is almost never sick. It is wandering — the normal, programmed end of larval life.

Keepers lose worms at this point by treating it as a problem: adding more food, adding moisture, moving them somewhere warmer. None of that helps and some of it hurts.

What Is Actually Happening

At the end of the fifth instar the animal has finished what it was growing for. The silk protein genes that ran hard from about day three to day five begin easing off. The gut empties. Feeding stops.

What replaces it is searching behaviour: the larva is looking for a site to anchor to and spin. In a rearing house that is what tells the operator to move worms to mounting frames. In a plastic cup it looks like distress.

What to Do

• If you are feeding them out: a wandering worm is at the end of its useful window. Use them.
• If you are breeding: move them to a pupating container with paper, mesh or crumpled card to grip. See how to breed silkworms.
• Either way: stop adding food. An animal that has emptied its gut on purpose does not want more.

How to Tell It From Illness

The distinction is usually clear once you know what to look for. A wandering silkworm is active, firm and purposeful. It moves with intent and often rears its head, searching.

A sick one is the opposite. Flacherie produces a limp, slack animal that has stopped feeding and stopped moving. Grasserie produces a swollen, shiny one.

Stopped eating and moving vigorously is a life stage. Stopped eating and gone limp is a problem.

Related: inside the silk gland · what silk is made of