Raising Silkworms: Care, Mulberry Chow, and Storage

All Angles Creatures

Silkworms (Bombyx mori) are unusual among feeder insects — they cannot eat anything except mulberry leaves or a mulberry-based artificial diet, they cannot survive without human husbandry, and they pupate on a strict 28-day schedule from hatch to cocoon. For keepers who want a steady supply of silkworms for their reptile collection (or who want to raise them through to moths for breeding), a few specific practices keep them healthy. Get those right and a batch will reliably produce strong, well-fed feeder larvae for two to four weeks. Get them wrong and silkworms die fast.

What silkworms eat — and why

In the wild, silkworms eat fresh mulberry leaves (Morus alba, white mulberry, primarily). 5,000 years of selective breeding have made them obligate mulberry specialists; they cannot survive on any other plant. Modern keepers rarely have access to fresh mulberry trees, so the standard food is mulberry chow — a paste made from dried, powdered mulberry leaves combined with water.

What mulberry chow actually is

Commercial mulberry chow is dried mulberry-leaf powder, typically with added agar or carrageenan as a binder, packaged as a dry mix. You combine it with hot water (per the manufacturer's instructions, usually a 1:3 to 1:4 ratio by volume), let it set for 5–10 minutes, and present it to the silkworms as small chunks or a thin spread. The cooled chow holds shape and stays firm enough that silkworms can climb onto it without sinking.

Fresh mulberry leaves as an alternative

If you have access to a mulberry tree (white, red, or black mulberry all work; Morus rubra and Morus nigra are equivalent), fresh leaves can replace chow entirely. Wash them, pat dry, and offer in handfuls. Silkworms love fresh leaves and grow faster on them — but the leaves must be pesticide-free and fresh; wilted or contaminated leaves kill silkworms quickly.

Daily care

Temperature

Silkworms thrive at 72–82°F (22–28°C). Below 70°F they grow slowly; below 60°F they die. Above 85°F they grow faster but become stress-prone. Never refrigerate silkworms — cold is the single most common cause of mass die-offs. A draft-free spot at room temperature is correct; a warm closet or shelf works fine.

Container and ventilation

The shipping container is fine for the first batch — usually a perforated plastic dish with the silkworms and chow already inside. For larger batches or longer-term keeping, a shallow plastic bin (10–14 inches across, 2–3 inches deep) with a vented lid works well. Silkworms don't climb well, so deep walls aren't necessary.

Cleaning

Silkworm waste (frass — small dark pellets) accumulates fast. Spot-clean every other day: shift the silkworms onto fresh chow and discard the old chow with the frass. A full bin cleaning isn't usually needed — the silkworms migrate to fresh food on their own.

Chow refresh schedule

Replace mulberry chow every 2–3 days. Old chow dries out, develops mold, or becomes too contaminated with frass to be safe. Mold is a silkworm killer — once mold appears, the entire bin needs to be cleaned and reset.

The 28-day silkworm lifecycle

Silkworms grow on a predictable schedule. Knowing where they are in the cycle helps you plan feedings:

Day 0–3: hatchlings, ~3 mm long. Eat constantly, grow rapidly. Most keepers receive silkworms at this stage or slightly older.
Day 4–10: first instar through second instar. ~5–15 mm. Soft, light-colored. Eat heavily.
Day 11–18: third and fourth instars. 15–35 mm. Visibly larger, light gray or beige. Best feeding-size range for most reptiles.
Day 19–25: fifth instar. 35–70 mm at peak. Still feeder-stage but getting large; appropriate for adult bearded dragons and panther chameleons.
Day 26–28: pre-pupation. The silkworms stop eating, become translucent, and begin spinning cocoons. Once they spin, they're no longer suitable feeders — feed them off in the days just before this stage.

Silkworms grow especially fast in the third and fourth instars. A small silkworm on Tuesday may be a medium silkworm by Friday. Re-evaluate sizing for your reptiles every few days.

Storing silkworms long-term

Silkworms can't be paused. Once they've hatched, they're on the 28-day clock and you either feed them off or let them pupate. Two strategies for keepers with smaller collections:

Order smaller, more frequent batches matched to your weekly feed-off rate. A 50-count of small silkworms feeds a single beardie for two to three weeks comfortably.
Stagger orders by 10–14 days so a fresh batch of small silkworms arrives before the previous batch matures past usable size.

You cannot freeze, refrigerate, or otherwise pause silkworm development. The lifecycle is the lifecycle.

Common keeper mistakes

Refrigerating "to make them last longer": kills them. Room temperature is correct.
Feeding non-mulberry plants: silkworms cannot eat lettuce, kale, dandelion, or any other green. Mulberry only.
Letting chow dry out: dehydrated chow is unpalatable. Cover the chow surface with a damp paper towel between feedings if humidity is low.
Mold: mold kills silkworms in hours. Spot-clean aggressively if you see any white fuzz or musty smell.
Overcrowding: silkworms need air circulation. Don't pack them tighter than ~30 silkworms per 10 sq inches of bin floor.
Pesticide-contaminated leaves: if using fresh mulberry, only use leaves from trees you control. Roadside or untreated-status leaves are too risky.

Letting silkworms pupate (optional)

If you want to breed silkworms or simply observe the lifecycle:

At day 25–28, silkworms stop eating and start searching for a place to spin. Provide a clean, dry area (paper towel works) where they can spin cocoons.
Cocoons take about 3 days to complete. Don't disturb during spinning.
Adult moths emerge 12–16 days after cocoon completion. They're flightless, blind, and live only a few days — long enough to mate and lay eggs.
Female moths lay 200–500 eggs each. Eggs need cold-storage (~50°F) to enter diapause if you want to delay hatching; otherwise they hatch in 10–12 days.

For most keepers, breeding isn't worth the effort — commercial silkworm prices are low enough that you're better off ordering fresh batches. But if you're interested in the lifecycle as a learning project, it's straightforward.

What to feed silkworms TO

Once your silkworms are healthy and well-fed on mulberry chow, they're nutritionally loaded for almost any insectivorous reptile:

Bottom line

Silkworms are not difficult to keep, but they are unforgiving when basic care fails. Room temperature, fresh chow every 2–3 days, no mold, and a quick re-evaluation of size every few days. Get those right and a batch reliably produces healthy feeders for two to four weeks. Browse our silkworm collection or read more in the Creature Insights blog.

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Published April 27, 2026 · last updated April 27, 2026