Why Silkworms Only Eat Mulberry

One Plant, and Only One

Bombyx mori is strictly monophagous: it eats mulberry leaves and essentially nothing else. That is not fussiness in the ordinary sense — it is a hard-wired feeding specialisation, and it is the single biggest practical constraint on keeping the animal.

Why That Is a Serious Drawback

Depending on one plant creates problems that have nothing to do with the silkworm:

• Mulberry is seasonal. Leaves are not available all year in temperate climates, which historically capped how many broods could be reared.
• Leaves collect what is in the air. Atmospheric pollution lands on them.
• They carry parasites. Wild foliage is not a sterile input.
• Pesticides transfer straight through. A mulberry treated with insecticide will carry it to the silkworms — and they are insects.

That last one is the one that catches keepers. A neighbourhood mulberry tree is an unknown chemical history, and there is no way to wash a systemic pesticide out of a leaf.

What Works as a Substitute

The reliable answer is mulberry chow — dried mulberry powder rehydrated before feeding — because it is still mulberry, just stabilised and storable.

Beyond that, work on alternatives has found frozen mulberry leaves effective, which is really the same solution by another route, and fresh organic iceberg lettuce has been reported as a workable stopgap. Treat lettuce as an emergency measure rather than a diet: it is a way to keep worms alive for a short period, not a way to raise them.

The Domestication Angle

Monophagy is not unique to silkworms — many caterpillars specialise. What is unusual is the combination: an animal that eats one plant, cannot fly to find it, will not disperse to look, and cannot survive without people. See the wild ancestor for how that stack of dependencies was built.

Related: raising silkworms at home · do silkworms need water?