10 Ways to Breed Silkworms

The best guide on how to hatch, tend & breed silkworms

When we think of domesticated animals, most of us picture farm animals, or maybe horses and camels. But every silk scarf you've ever seen was made by a domesticated animal too: the tiny silkworm. Humans have been breeding these insects for silk for over 7,000 years.^{[1]XResearch source} At this point, the silkworms are so used to it that just about anyone with a warm room can look after them. This is an especially fun project for children, or anyone who wants the chance to care for an underappreciated kind of animal.

Question 1 of 10:

How do you get silkworm eggs?

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You can order eggs online. They're available at any time of year.^{[2]XResearch source} You can order breeds with different patterns or that make different colored cocoons, but they're all raised in basically the same way.
- The eggs start out at tiny, yellow dots. By the time they get to you, they'll probably be gray-green, gray-purple, or light brown. If you see a different color, you might have eggs with a rare mutation!^{[3]XTrustworthy SourcePubMed CentralJournal archive from the U.S. National Institutes of HealthGo to source}
- The silkworm is a domesticated species that doesn't exist in the wild.^{[4]XResearch source} If you see its wild relatives on mulberry trees in East Asia, leave them on the tree—they can't be bred the same way.^{[5]XResearch source}

Question 2 of 10:

Where should you keep silkworm eggs?

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Keep the eggs in a small container in a warm, well-lit room. A petri dish or a shoebox are common choices. The eggs will hatch fastest at around 29ºC (84ºF), but they'll eventually hatch at room temperature too.^{[6]XResearch source}
- Careful—they like a warm room, but direct sunlight is too much heat.^{[7]XResearch source}
- The eggs don't do well if they're super dry or super moist. If the room is dry, try adding a little square of damp paper to the container, but not touching the eggs. If the container is damp enough that drops form on the sides, move it somewhere drier.^{[8]XResearch source}

Question 3 of 10:

How long do silkworm eggs take to hatch?

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1
About one to three weeks depending on temperature. If the temperature is perfect (about 29ºC / 84ºF), the eggs can hatch in as little as nine days.^{[9]XResearch source} At room temperature, your eggs might take up to three weeks.^{[10]XResearch source}
- It's normal for some eggs to fail to hatch. Blue eggs that fail to hatch might be a sign that the eggs weren't handled right, so try ordering from a different supplier next time.^{[11]XResearch source} (But some blue eggs can still hatch, so don't give up them.)
2
Eggs can also keep overwinter in a warm fridge. Many silkworms only reproduce once a year, and their eggs do best when they stay dormant until the next spring. If you successfully breed the silkworms, it's usually best to keep the new generation of eggs in the refrigerator until next spring. Keep the fridge temperature above 10ºC (50ºF) to avoid killing the eggs.^{[12]XResearch source}
- This temperature is higher than the standard food-safe fridge temperature, so use a separate mini-fridge
- If your silk worm breed was labeled "bivoltine," "polyvoltine," or with a number 100 or above, you could try to breed multiple generations per year, between spring and fall. Even then, the breeding schedule isn't guaranteed, since it's affected by heat and light.^{[13]XResearch source}

Question 4 of 10:

What's the best place to keep silkworm larvae?

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Keep them in a warm container with paper towels and holes for air. Your silkworms can live their whole lives in a shoebox about 6 inches (15 cm) deep. Just poke plenty of holes in the lid for air, and line the container with paper towels.^{[14]XResearch source} A plastic or glass container is a bit worse than cardboard, because it's harder to get airflow and can overheat more easily.^{[15]XResearch source} Silkworms love a warm (but not hot) home: always keep them above 20ºC (68ºF), and ideally around 27ºC (81ºF).
- Newly hatched silkworm larvae are tiny squiggles. If you hatched the eggs in a petri dish, you can catch the squiggles on the end of a fine tip paintbrush to move them.^{[16]XResearch source} It's also fine to put the whole petri dish in the box.
- The larvae start out very small, so one container to start with is fine. If they start to get overcrowded as they grow, move some to a second container.
- Giving the silkworm larvae indirect sunlight during the day is nice if you can manage it. Silkworm larvae do react to light, and will feed more if they have light during the day and darkness at night.^{[17]XResearch source} That said, the silkworms won't die if you keep them in the dark.^{[18]XResearch source} Just be careful not to put the container in direct sunlight, which can overheat them.^{[19]XResearch source}

Question 5 of 10:

How do you feed silkworm larvae?

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1
Mulberry leaves are best, but not available year-round. You'll need two types of leaves. Thin, tender, young mulberry leaves are the only ones the youngest silkworms can eat. Thick, juicy, dark green leaves are better for older larvae.^{[20]XResearch source}
- If you can't get the young leaves, use artificial food and switch to mature leaves later.
- Ask the people who sell the leaves whether good-quality leaves will be in season until at least 24 days after the eggs hatch.^{[21]XResearch source} If not, it's better to use artificial food the whole time instead. Silkworms fed on mulberry leaves sometimes won't accept artificial food later.^{[22]XResearch source}
This should come with instructions that tell you how to prepare it before feeding your silkworms, and how much they eat. Food is the only way that silkworms get water, so make sure to replace it as soon as it dries out.^{[23]XResearch source}
3
Wash the mulberry leaves before feeding. Leaves can carry diseases or pests. Wash them under running water, then shake dry and store them in the fridge in plastic bags.^{[24]XResearch source} (A little damp is fine, but silkworms don't want soggy leaves.) Before each feeding, throw away any yellow or dried up leaves.^{[25]XResearch source}
- It's even better to go the extra mile and disinfect them.^{[26]XResearch source} To do this, add 3 tablespoons (44 mL) of bleach and a drop of dishwashing detergent to 1 gallon (3.8 L) of water. Soak the leaves for three minutes, then rinse them very thoroughly under running water. (Any soap left can kill the larvae.) Shake dry and store in plastic bags in the fridge.
4
Start with one leaf a day, then increase as they grow. Wrap the stem of a mulberry leaf in a scrap of moist paper towel and put it in the container. Replace this at least once a day. After a few days, start putting in several leaves bunched together instead.^{[27]XResearch source} Use enough leaves (or replace them often enough) that the silkworms always have access to fresh food.
- For the first couple days, use a soft paintbrush to very gently pick up the tiny, newly hatched larvae and move them off of the old leaf, then onto the new one.^{[28]XResearch source}
- If the newly hatched larvae aren't eating, the leaves might be too thick. Try slicing them as thinly as you can and sprinkling them into the container, or switch to artificial food.^{[29]XResearch source}

Question 6 of 10:

How do you clean the silkworm habitat?

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Brush out the feces, old food, and skin molts every other day. Leaving it in there too long can cause mold or bacteria to grow.^{[30]XResearch source} For the first few days, when the larvae are tiny, you can use a small paintbrush or a small spoon to clean around them. Once they're larger, you can pick them up and move them to a temporary box while you clean.
- It's best to leave the larvae alone while they molt. In each molt, they rest for about a day, staying still with their head held up before shedding their skin.^{[31]XResearch source} Let them snooze and come back to clean tomorrow!
- Don't wash with water and especially not soap, which can kill the larvae. The life cycle is only a few weeks long, so you can wait until they're in cocoons before you do a thorough clean.

Question 7 of 10:

How do you get the silkworms to cocoon?

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1
Put in sections of toilet paper roll when the larvae turn translucent. Silkworm larvae usually molt four times, then spend a final six or seven days feeding before they're ready to make a cocoon. Their bodies then turn a little translucent, and they stop eating. When they roam around and keep raising their heads up, they are looking for a place to spin cocoons.^{[32]XResearch source} Help them out with a cardboard toilet paper roll cut into circles, or move them into rolled-up paper towels or newspaper and twist the ends closed.^{[33]XResearch source}
- If some of the silkworms have already started to spin silk, leave those ones alone. Interrupting the spinning can kill them.^{[34]XResearch source}
2
The transformation into moths takes 8 to 14 days. This doesn't include the two or three days it takes to finish spinning the cocoon.^{[35]XResearch source} Leave the cocoons undisturbed to give the silkworms the best chance to turn into healthy adults.
- After two or three days of spinning, the silkworm inside spends another two or three days pupating. After this point, you can cut open the end of a cocoon with a razor blade, and gently pull out the pupa (for instance, to show them to a science class). If you are very careful and return the pupa to the cocoon, it can still become a moth.^{[36]XResearch source}
- The moths usually come out in the early morning, so start waking up early if you want to be there when it happens.^{[37]XResearch source}

Question 8 of 10:

How do silkworms mate?

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You can tell the sexes apart by their size (females are larger) and behavior (males move faster and flutter their wings more).^{[38]XResearch source} While mating, they face away from each other and join the ends of their bodies.^{[39]XResearch source} After mating, the female lays hundreds of eggs.^{[40]XResearch source}

Question 9 of 10:

Do I need to look after the silkworm moths?

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The moths don't need food or any other care. Adult moths can't eat and only live for between 3 and 10 days.^{[41]XResearch source} All that's left to do is appreciate them while they're still around.
- Silkworm moths can't fly, so you can take off the lid to look at them without much risk of them escaping.^{[42]XResearch source}

Question 10 of 10:

Can I cross-breed different types of silkworms?

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Yes, you can cross-breed to make new strains. Silkworms of different strains will mate with each other, and their children might look different or make different sizes or colors of cocoons. Keep in mind that cross-breeding silkworms for a specific purpose (like larger cocoons or healthier larvae) takes a lot of training and experience.^{[43]XResearch source}
- If you want to experiment, it's usually more consistent to cross-breed in spring. If you can, separate the sexes so you can combine the males of one strain with the females of another. (The male larvae are usually bigger and can have different markings, but it's hard to tell in some strains.^{[44]XResearch source})

Community Q&A

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Question
Can spray or smoke kill the silkworm? How can protect them?
Community Answer
Smoke cannot, but bug spray can. So, keep them clear of anywhere someone might spray.
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Can I feed them anything other than mulberry leaves?
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Yes, you can feed them mulberry chow, but that's the only good alternative.
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Do I have to put the eggs in the refrigerator?
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No, just make sure they are submerged in dirt in a cool place, and make sure the dirt is moist. Spray it with water every 2 days.
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Tips

Silkworms go through cycles of feeding and molting, so don't worry if they start eating less.^{[45]XResearch source}
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If you're raising a lot of silkworms, you can use a big tub with a removable mesh floor. Most of the silkworms will stay above the mesh (where the food is), so you can take the whole mesh out to get easy access for cleaning.
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If there are water droplets on the sides of your container, poke more air holes or move them somewhere with more air flow. Bad ventilation can cause a mold or bacteria infection.
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Warnings

Most places have legal restrictions when it comes to throwing away non-native species, even dead ones. One way to deal with dead eggs, larvae, and moths is to freeze them thoroughly, then throw them away inside a sealed plastic bag.^{[46]XResearch source} But it's best to check local laws, especially if you are raising silkworms for a school or other institution.
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Soap can kill the larvae. If you clean a container to use as a habitat, wash it a second time thoroughly with plain water.^{[47]XResearch source}
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Things You'll Need

Silkworm eggs
Tender, young mulberry leaves (or artificial silkworm food)
Mature, thick mulberry leaves (or artificial silkworm food)
A fine-tipped paintbrush (for moving young larvae)
A shoebox or similar container
A second, temporary box (to store larvae while cleaning their main habitat)
A warm location away from direct sunlight
Cardboard toilet paper rolls, newspaper rolls, branches, or other surfaces to spin cocoons on
Fridge
Sealable plastic bag