Raising Silkworms

Silkworms (Bombyx Mori) are honestly a great “livestock” for a homesteader–urban, suburban, country, what have you. This is especially true of those of us who have access to mulberry trees, which are relatively common on Long Island. Even for those who do not, commercial food options exist in such abundance that we can raise them anywhere, and in any season. The only things these little creatures need are a container, food, and cleanliness. They breed readily, and provide the silk cocoons for which they are named. They are the only truly domesticated insects and cannot survive outside of human care–once in their moth stage, they do not have the ability to fly, nor eat, and their sole purpose is to breed.

You can buy your own from breeders, or from commercial suppliers that sell them for reptile consumption–they are exceptionally high in protein and all sorts of critters find them delicious and nutritious to eat.

Aside from the aspect of being able to produce thread and yarn, they are an amazing learning experience for children. The only reason I started raising silkworms again was because my 4 year old daughter asked for them, and I realized I forgot how much fun they are to keep!

Not only that, but they are a source of income–those who like using fibers to make things will pay good money for well processed cocoons. As of 2017, 25 high end cocoons can fetch $16, and for something that you can easily raise thousands at a time with very little space and effort, it’s a wonderful thing to supplement your income with. Likewise, 50 small silkworms to be used as reptile food is around $15.

The worms come in two visual colors–striped and all white. It makes no difference but I like to separate them so they breed true.

History

There is a lot of folklore surrounding the history of the domestication of silkworms. They are descended from their wild counterparts Bombyx mandarina, and can often hybridized if allowed. This is important because in the event of a genetic or disease issue with domesticated stocks of Bombyx mori, this outbreeding can help increase variety in the gene pool.

They were first domesticated 5,000 years ago in China. The story of their domestication is mostly myth, but I grew up hearing it in my Chinese classes (my teacher, who is like a second mother to me, still teaches and I often send her silkworms to show students.) It goes that the legendary empress, wife of the Yellow Emporer, Leizu (also known as Xi Ling Shi) had collected some cocoons that she found lovely and accidentally dropped one in her tea. When she hurriedly fished it out, she found that it unwound and produced a lovely thread. She then asked her husband to plant a grove of mulberry trees where she can raise some more. She is credited with the discovery of sericulture–the cultivation of silk.

Silkworm raising is a childhood past time for many kids in China and Taiwan. They compete to see who can raise the biggest, fattest caterpillars, keeping these prized pets in bamboo canisters. My mom remembers how mulberry leaf peddlers would sell children 5 leaves for 1 TWD, and how she only now realized what a ripoff that was. It’s still a dear memory for her though, and it’s a lovely look into the culture of Asia. Children were warned that the leaves they feed their worms must be washed and wiped dry, or the water could cause their pets to get sick and die–that is not exactly true although it can happen, I’m pretty sure it was to teach the kids more responsibility. My mom freaked out when I presented my worms with unwashed leaves, and was still skeptical even as they grew on them. I guess deep, childhood beliefs are long lasting. (You should still wash them in case wild moth populations carry diseases/viruses that could harm them. I didn’t because I was lazy and thankfully nothing happened. I do wash them now.)

The kanji character for silkworm is 蚕, combining the character for heaven 天, and insect/bug/worm 虫, so it is said that silkworms are heavenly creatures requiring respect and love. Some even say they are descended from fairies! I can imagine the cute little moths fluttering around must have inspired this idea. Supposedly, if you insult them, they will disappear!

Life Span

The eggs of the silkworm, usually stuck on pieces of paper that were provided to the parents, are taken out of cold storage and kept in a warm area (above 72 degrees Fahrenheit) to incubate. After about 14 days, the tiny caterpillars emerge and begin eating the tender new mulberry leaves. They much prefer white mulberry, as opposed to black or red, but all three can be provided as food and will be accepted.

When they first come out, they are black and covered in hair, earning the name “Kego” or “Fuzzy Baby” in Japanese. It takes about a month (26 days, give or take) from hatch for them to start spinning their cocoons and pupate, and another 3 weeks for them to become moths. In that time, they will have grown from tiny caterpillars barely bigger than the head of a pin, to one that’s about the size of your index finger. They will also have molted their skin four times, each period of their lives between molts called an “Instar,” the 5th instar after their 4th molt being the last one before pupating.

Finally, the moths, fluffy, white, with large, dark eyes look for a mate and breed, laying thousands of eggs. These eggs are placed into a cold storage area for about 2-4 weeks to simulate a winter, which will trigger them to hatch, and they remain viable supposedly for up to 5 years. I’ve had them last 2, so I can’t say if they really will last for 5.

Harvesting Silk

Usually, in order to create unbroken silk thread, the cocoons are boiled with the pupae still inside, since if allowed to emerge, the moths will have broken a hole through the cocoon. Some animal rights activists and Buddhists are against this method, and so “Peace” silk has been developed in response, where the moths are allowed to emerge and the cocoons are processed as thread or yarn after.

Whatever the method, the cocoons are boiled with soap and water to “degum” it (removing the sericin, which makes up 25% of the weight), the impurities removed, and then spun into whatever form is desired.

Some silkworms have been selectively bred to create cocoons so thick that they cannot escape without help.

You can also make “silk soap” with the silk–sericin being reportedly great for skin (although there is a lot of debate as to whether how effective it can be absorbed through the skin.)

For Consumption
Silkworm pupa is eaten as a delicacy in many parts of Asia. It is very high in protein and while a acquired taste, it is widely enjoyed. Frying them is a better method for those who are squeamish. I can safely say I joined the ranks of trying them for culinary purposes. You can read about the account here.

The feces of the silkworm is also sometimes made into an herbal tea, or dried and used as a filling for pillows. Don’t worry, it doesn’t smell bad–grassy, like dried mulberry leaves.

Their poop is also excellent compost to mix into your flower beds!

Raising Silkworms At Home
I keep mine in whatever container I happen to have on hand, with holes punched out to release humidity and give oxygen. Sometimes if the container big big enough, I don’t bother covering it–they don’t wander until they’re looking for a place to spin. During the summers, I collect the mulberry leaves from my backyard (a neighbor’s white mulberry largely overhangs my fence) and during the winter months, I will use the commercially prepared food.

You can freeze the leaves too, although they will turn into a texture similar to blanched spinach. The silkworms will still eat them, but they may not be too fond of it at first.

Once you feed them leaves, it may be difficult to turn them back to the commercially prepared food, but I have done it during changing seasons with success.

When they are ready to spin their cocoons, they will expel the contents of their digestive systems, shrink somewhat in size, and begin looking for a place to spin. I either make paper rolls or, if I have any left (I use them for tinder), toilet paper rolls. You’ll know they have finished spinning when you shake the cocoon lightly and hear the pupa rattle inside of it. At this point you can either process them or wait for them to emerge and breed.

You can select the largest cocoons and place them together if you want to selectively breed bigger cocoons (which equals more silk per worm.) When they emerge, the females will be large and plump, full of hundreds of eggs. The males will be small, their abdomens not distended, and they will excitedly vibrate their wings as they walk around looking for a mate.

Once found, the male will position himself so that their ends connect. After a little while, they will disconnect and the female will begin laying the eggs on whatever you give them. I like to provide white paper to see it easily. She will lay them in tight clusters as she moves, and the eggs will be glued onto the surface in one layer.

If the eggs were fertilized, they will turn dark gray after 1-3 days, at which point you can put them in cold storage. I put them in zip lock bags and stick it in one of the drawers of my fridge (not the bottom ones which might risk freezing.) After two to four weeks, you can take them out and start another batch. The tiny kego will need tender new leaves or slightly softer (add a bit more water) silkworm chow. Grating it will help the pieces stay small and thin for the little silkworms to be able to process it. The whole process then starts again! Be careful not to allow condensation to build up in their containers because they will drown in the droplets of water. They’re that tiny!

These days, interesting silkworm food are available that makes the spin colors (like green, blue, or pink.) Some silkworms naturally spin sunshine yellow cocoons. However, the colors wash out during processing, but some scientists are attempting to create food that make them spin permanently colored silk! Since the dyeing aspect of silk is harmful to the environment, this would be a great alternative.

Cleanliness Is Next To Godliness
Silkworms have a reputation for needing clean spaces, which really just means you have to remove the poop and uneaten food every day so it doesn’t mold.

Remove any silkworms that seem to be discolored or leaking fluids as they may be sick and can destroy an entire batch. You can put them in a quarantine box, and make sure to wash your hands thoroughly before and after you handle any sick worms. Practicing good hygiene will help you have successful batches.

Homemade Silkworm Chow
There is a recipe for it online but I have not tried it yet. If you have and it works, please let me know! I have included the recipe below. I am attempting to create a different recipe, and will update if it’s successful as I think the ratio of soy flour and cornmeal are too high to the mulberry leaves and may not be necessary as they seem like fillers/binders.

29 ounces of mulberry leaves, fresh. Dehydrate and mill into fine powder in the food processor.
28 ounces Soy flour
6.1 ounces Corn meal

Mix the dry ingredients together and store until use. Boil it with water and then chill before use.

November 1st, 2017
Experimenting With Home Made Silk Worm Chow
I made my own recipe which has been readily accepted by the silkworms but only time will tell if they will grow and pupate on it. It smells very similar to the commercially bought chow, although the mulberry scent is much stronger. I noticed my powder isn’t as fine as the commercially available ones, but the silkworms seem to prefer this since they have an “edge” to start chomping on.

Mine was 2 lbs fresh mulberry leaves, dehydrated and milled into a fine powder in the food processor (about 1 cup.)
2 Tablespoons all purpose flour
1 Tablespoon corn starch
1 Tablespoon Whey Protein Powder

For one tablespoon of this chow, I added 2 tablespoons water. Then into the microwave and heated until it has formed a thick paste. Cool and give to silkworms. May not keep for more than two or three days with the silkworms so make sure they eat it all before you give them more. May keep up to a week in the fridge.

I’ll update in the coming weeks if they have thrived on it.

Update: November 10th, 2017
I need to find a better binding agent for the home made chow, since while they eat it readily, they also apparently roll around in it so much that it gets smeared on them, dries, and then it kills them through mold or covering their breathing holes. Maybe agar or more flour/soybean flour.

Once I found that was happening, I removed my home made chow and mixed it in with the commercial (since they have larger amounts of binding agents). Mixed, the silkworms still eat it, and have started to spin their cocoons on it.

This might be a good way to stretch the commercial food.