Silkworm Care for Beginners: A Practical Guide

I keep silkworms for one reason above all: they're the gentlest premium feeder I can hand a reptile. Soft-bodied, high in moisture, no hard exoskeleton to fight, and almost impossible to escape since they barely move and can't climb out. They're also genuinely fun to raise, you watch a tiny hatchling become a fat caterpillar and then a cocoon in about a month. Here's how to do it without losing the batch.

Know the life cycle you're managing

Silkworms are Bombyx mori, the domesticated silk moth, and they run a clean four-stage cycle. Understanding it tells you what to do at each step.

The larval stage is the whole game for a feeder keeper. The moths can't fly and don't feed; they exist to make the next generation of eggs.

Dial in temperature and humidity

Silkworms thrive at 75-85°F. Push toward the mid-80s and they grow noticeably faster; let it drop into the 60s and growth crawls. Steady is more important than perfect, they dislike swings and drafts, so don't park them by a window or a vent.

Aim for moderate humidity, roughly 60-75%. Too dry and the leaves wilt fast and the worms dehydrate; too wet and you're inviting the mold and bacterial diseases that wipe out silkworm batches. A hygrometer takes the guesswork out. If your air is dry, a damp sponge or cloth nearby nudges humidity up without wetting the worms directly.

The container and keeping it clean

A shallow, ventilated container is all you need, a plastic shoebox or a mesh-lidded tub. The non-negotiables:

• ◆Airflow so moisture doesn't build up and breed mold.
• ◆A paper liner on the bottom. This is the trick that makes daily cleaning trivial: lift the old liner, droppings and all, and lay a fresh one.
• ◆No overcrowding. Crowded silkworms compete for food, foul their space faster, and pass disease more easily. Give them room and split them into a second tub as they grow.

Cleanliness is the difference between a thriving batch and a sudden die-off. Silkworms are sensitive, and frass plus old leaves turn into a bacterial soup fast. Clear uneaten leaves and droppings daily, and wash your hands before handling them.

Feeding: it's mulberry or mulberry chow

This is the part people get wrong. Silkworms eat fresh mulberry leaves (Morus species, classically Morus alba) as their natural diet, and that's it, they won't substitute random salad greens. The practical options:

• ◆Fresh leaves: bright green, pesticide-free, rinsed and fully dried before going in (wet leaves cause disease). Chop them fine for newly hatched worms; offer whole leaves as the worms get bigger.
• ◆Silkworm chow: a powdered mulberry-based diet you mix and steam. This is what most keepers actually run year-round, because fresh mulberry isn't available everywhere in every season. It works well and keeps the bin tidier.

Feed multiple times a day, silkworms have a high metabolism and eat constantly. Never let them sit foodless for long stretches. Store spare fresh leaves wrapped in a damp cloth or bagged in the fridge to keep them from wilting.

Sourcing good eggs or worms

If you're starting from eggs, look for small, uniform, grayish-purple ones; avoid cracked, discolored, or oddly shaped eggs. Buy from a supplier who labels the strain and stores eggs properly (cool, ~50-60°F, until you're ready to incubate). Note whether eggs are diapause-treated, that determines whether they need a temperature trigger to hatch. For most beginners, buying small worms already feeding on chow is the easiest on-ramp; you skip the hatch and go straight to growing them out.

Watch for the common diseases

Silkworms are hardy when clean, but a few classic problems show up when conditions slip:

• ◆Grasserie (a viral infection): swollen, shiny, fragile body; lethargic worms that may rupture when handled. Spreads through contaminated food and surfaces, hygiene is the defense.
• ◆Flacherie (bacterial): worms go off their food, turn soft, and die. Driven by poor-quality leaves and damp, dirty conditions. Fresh dry leaves and a dry, clean bin prevent it.
• ◆Pebrine (a parasite): dark spots and sluggishness; essentially untreatable, so cull affected worms and start clean.
• ◆Fungal/mold infections: from excess humidity and poor airflow; control moisture and ventilate.

The pattern is obvious: most silkworm losses trace back to wet, dirty, crowded, or chilled conditions. Fix the environment and you prevent most disease before it starts. Isolate any worm that looks swollen, discolored, or mushy right away.

As a feeder: soft, but still needs calcium

Silkworms shine as feeders precisely because they're soft and high in moisture, easy to digest, great for hatchlings, picky eaters, and animals recovering from impaction. They're often praised as nutritionally favorable, and they are a good choice, but don't assume they're a complete mineral package. Like virtually all feeder insects, silkworms still skew phosphorus-heavy, so dust with a calcium supplement before feeding insectivorous reptiles and amphibians to support bone health and prevent metabolic bone disease. (Black soldier fly larvae are the one feeder with a genuinely calcium-rich profile, silkworms are not that exception.)

If you want cocoons instead of feeders

Letting a batch go to cocoon is rewarding. Worms signal readiness by wandering and emptying their gut around five weeks in; give them clean, dry surfaces or cardboard structure to spin on. They spin for 2-3 days. If you're after intact silk or breeding stock, handle cocoons gently and store them dry and ventilated. If you'd rather let moths emerge to lay the next generation, just leave the cocoons undisturbed for two to three weeks.

If you'd rather buy silkworms ready to feed (or grow out) than hatch your own, All Angles Creatures stocks silkworms and chow. For the biology behind the species, the University of Michigan's Animal Diversity Web entry on Bombyx mori is a solid non-commercial reference, and for the calcium-supplementation side, see the Merck Veterinary Manual on reptile nutrition.

Building a varied feeder rotation? Compare options in superworms vs mealworms, and for a self-sustaining colony see breeding discoid roaches.