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On the theme of remarkable discoveries from humble insect beginnings, let’s explore another insect that also changed human history, the silkworm.

Legend has it that humans and silkworms met one fine morning in the year 2640 B.C. A Chinese Empress named Hsi-Ling-Chi (various other spellings found) was strolling in her garden drinking tea when a white cocoon plopped into her cup from an overhead tree.

It probably looked something like this:

silkworm cocoon

Instead of dumping it out and asking her servant for another cup of tea like any reasonable person would probably have done, she studied the cocoon. She stirred the warm tea with her finger and noticed a fine strand beginning to unravel from the fuzzy cocoon. Being a weaver, she thought of using the fiber to make cloth. She called to her servant and together they unwound the cocoon into a single long filament. Thus, the silk industry was born.

The cocoon that Hsi-Ling-Chi had collided with was that of the silkworm moth, Bombyx mori. The caterpillar feeds on leaves of mulberry trees of the genus Morus, hence the silkworm species name mori.

silkworm caterpillar

Here are some silkworm caterpillars getting ready to pupate:

silkworm caterpillar

When it is ready to transform into an adult, the caterpillar uses its enormous silk-producing glands (the glands are up to 25% of the mature caterpillar’s weight!) to spin the oval cocoon.

Rather than being soft and pliable, as you would expect from something made of silk, the cocoon is actually rigid because the caterpillar adds a sticky, gummy protein called sericin to the thread. The sericin hardens into a stiff protective coating, giving the whole thing a consistency resembling Styrofoam. Inside the cocoon, the caterpillar transforms into a pupa, and then into a buff-colored moth.

How does a moth, which does not have chewing jaws like the caterpillar, escape the hardened cocoon? Amazingly, the moth discharges a special enzyme that dissolves both the silk and the sericin in one end of the cocoon, allowing the moth to escape through a circular opening.

With her swirling tea bath, Hsi-Ling-Chi had discovered the process to free the silk from the sericin by immersion in hot water. If the moth is allowed to emerge from the cocoon naturally, the enzyme cuts through all the strands, making too many short pieces to spin easily. In the silk industry the cocoons are boiled with the pupa still inside to obtain one long strand of silk, exactly as the caterpillar laid it down. Strands from several cocoons are then spun together to make a strong thread, and woven into cloth.

The resulting silk cloth was like nothing that had been available before. It was lightweight and relatively smooth, and pleasing to the touch. The Emperor soon realized the potential of silk as a commodity and rushed into large-scale production. The Chinese began to share their product with the world, which was eager to buy it.

Although they were willing to sell the silk cloth, the Chinese carefully kept the source shrouded in mystery for well over 1000 years. The penalty for disclosing the source of silk was death. By keeping silkworms a secret, the Chinese developed one of the greatest trade monopolies ever. Wealthy Europeans and Middle Easterners wanted the silk, and the so-called Silk Road between China and Europe opened up more trade between the continents. Other products and ideas began to be exchanged as well. This exchange of goods allowed certain groups to accumulate wealth and shifted power and culture throughout the world.

Speculation about the source of silk was wild. One group thought the Chinese were harvesting silk from a new variety of animal called a sea-sheep. Others thought it came from various plants. As late as the Roman Empire, Pliny the Elder who wrote his Natural History around 70 AD, thought the source of silk was a tree. Eventually Japan, India and then the Byzantines discovered the real secret of silk and started their own silk production or sericulture programs. The Byzantines were able to undercut the Chinese after some Nestorian monks smuggled silkworm cocoons out of China in their canes. But China remained the most important source for many centuries. Eventually the Turks cut off the overland route to Asia. European exploration for alternative routes to obtain both silk and spices lead Columbus to the New World.

Early Europeans coming to the New World carried silkworms with them. The English had long wanted to develop a silkworm industry, but their climate was not suitable. The king thought that starting silkworm farms in the colonies could be a good solution and forced farmers to plant groves of mulberry trees. However, the silkworms turned out to be fussy and never did well. Farmers quickly turned to more profitable cotton and tobacco as crops.

Not only did the silkworm change our history, but we changed the silkworm too. Silkworms are now truly domesticated creatures. There are no Bombyx mori moths left in the wild. Over thousands of years of selection by humans, the caterpillars have lost all urge to crawl and sit placidly waiting for food to be dumped onto them. The moths are heavy-bodied with shortened wings, and they can do no more than flap their wings and make short hops. When we raised ours, we found that if a male moth managed to flutter out of its container, it sat there (I thought it looked embarrassed) until a person comes along to retrieve it. Silkworms now depend on humans completely for their survival. Some strains have been bred that can develop on artificial diets made of ground up dried mulberry leaves and vitamins.

Along with the changes in the people and the moths, came changes with the trees they feed on. Because the silkworm consumes leaves of the mulberry tree, particularly the white or Chinese mulberry Morus alba, the trees were spread throughout the world with the silkworms. In the United States we also have a native American or red mulberry, Morus rubra, and the black mulberry, Morus nigra, first sent over from Europe during the colonial period. White mulberries of the variety Morus multicaulis were developed for silkworm cultivation and have been distributed widely during attempts to establish a silkworm industry here. In addition to being food for silkworms, the trees produce small clustered fruit that can be used to make jams, pies and fruit spreads.

mullberry treemullberry tree

Eventually synthetic fibers were discovered that have largely replaced silk. Nonetheless, it is still a popular fabric. It takes dyes beautifully, is warm in winter, cool in summer and drapes marvelously. Today silk is still cultivated in Japan, China, Spain France, Italy and Columbia. Lady Di’s wedding dress was made of silk from Britain’s last remaining active silkworm farm. Throughout the last 4000 years wearing silk has been a status symbol of the wealthy, and the desire for it has changed history.

For more information on rearing silkworms, a step-by step look at growing silkworms can be found in the Bombyx mori on-line Journal.

Edit: For more recent photographs, see a newer post about silkworms.

Books (linked titles and images go to Amazon):

Children's Nonfiction:

Silkworms (Lerner Natural Science Books) by Sylvia A. Johnson

Silkworm (Life Cycle of a . . .) by Ron Fridell, and Patricia Walsh

The Story of Silk: From Worm Spit to Woven Scarves (Traveling Photographer)by Richard Sobol

Children's Fiction
The Empress and the Silkworm by Lily Toy Hong

Fiction Chapter Book

Project Mulberry by Linda Sue Park is a fiction chapter book about two children who decide to raise silkworms for a state fair project. Although the story about silkworms is already compelling, the main character and the author also have chats on the side throughout the book that reveal how the process of writing works.

Adult Non-fiction:

Shrinking the Cat: Genetic Engineering Before We Knew About Genes
by Sue Hubell. Houghton Mifflin Company, New York. 2001. Despite the title, she also has packed in a great deal of information about silkworms.

Science Books for Kids also has a growing list of children's books about moths and butterflies.

In a previous post on theme gardens for children, I promised to dig up (ugh!) some relevant books. I finally got a chance to put them together.

Here are two of our favorite gardening books:

Jack's Garden by Henry Cole

This lovely book is a retelling of the nursery rhyme “This is the House that Jack Built,” using a gardening theme. It starts with tools a gardener would use, then critters you would find in the soil, all the way to a mature garden with birds and butterflies. Even though it is a picture book with few words, the illustrations are so rich it can be used with almost any age. Wonderful book!

Pumpkin Circle: The Story of a Garden by George Levenson, Shmuel Thaler (Photographer)

When I lent this one to someone and never got it back, I knew I had to go out and buy another copy. This book is really one of a kind. The photographs are exceptional. (Although they do have a flower fly identified as a honey bee. This is a common mistake.) The website has good information, too.

(If you are in the mood for more books about apples and pumpkins for fall, check this list of fall-inspired books from the MissRumphiusEffect Blog.)

Books on Theme Gardening with Children by Categories

1. ABC Gardens:

Garden Books with Alphabet Themes

A Cottage Garden Alphabet by Andrea Wisnewski

Centered on a garden, the book goes through the alphabet: A is represented by an arbor; C is a cottage; I is iris; Z is zucchini. The pictures, which look like woodcuts, are actually hand-colored paper cuts and the author discusses how she makes them.

Alphabet Garden by Laura Jane Coats

A Gardener's Alphabet by Mary Azarian

Patty's Pumpkin Patch by Teri Sloat

Follow the progress of a pumpkin patch through the seasons while finding items from the alphabet. For example, in the field where the pumpkins are being planted, “a” is for ant and “b” is for beetle.

2. Rainbow Gardens:

Blue Potatoes, Orange Tomatoes by Rosalind Creasy, Ruth Heller (Illustrator)

If you are interested in planting a rainbow garden this book could be a helpful resource. Ruth Heller is definitely one of our favorite authors and illustrators.

Planting a Rainbow by Lois Ehlert

This beautiful book lists many flowers of different colors.

3. Animal Gardens

Waiting for Wings by Lois Ehlert
I already mentioned this one in the butterfly/moth book post, but it is definitely worth mentioning again here. This is a lovely book, full of good information.

Bird and Wildlife Garden Books for Adults

The Bird-Lover's Garden: Creating a Backyard Haven for Songbirds and Hummingbirds by Margaret MacAvoy, and Pat Kite

The Audubon Backyard Birdwatcher: Birdfeeders and Bird Gardens by Robert Burton and Stephen Kress

The Wildlife Gardener's Guide (Brooklyn Botanic Garden All-Region Guide) by Janet Marinelli, Steve Buchanan (Illustrator)

4. Food Themes

Grow Your Own Pizza: Gardening Plans and Recipes for Kids by Constance Hardesty, Jeff McClung (Illustrator)

The title says it all for this fun book.

Gardening with Children by Beth Richardson

Tells how to grow a pizza garden, among other things.

5. Story Books

Linnea in Monet's Garden by Cristina Bjork, Lena Anderson (Illustrator), Joan Sandin (Translator)

If you are interested in art, artists, Monet, nature, gardening or traveling to Paris, this is the book for you. Definitely inspires me to want to grow a “Monet Garden” of my own. Beautiful, sweet, and informative, I keep our copy with the art books, but it wants to be with the nature and gardening books, too.

The Secret Garden by Frances Hodgson Burnett, Tasha Tudor (Illustrator)

6. Heritage/Cultures

Corn Is Maize by Aliki

This book is part of the Let’s-Read-and-Find-Out Science series. It has a wealth of information about many aspects of corn, including how it was first domesticated by Native Americans.

For Adults:

Buffalo Bird Woman's Garden: Agriculture of the Hidatsa Indians by Gilbert L. Wilson

Amazon review (edited): This book is rich with useful gardening lore, including tools and structures, and detailed descriptions of the different kinds of beans, corn, and squash that the Indians grew. Plus, there are native recipes you can try. Okay, I put this on the list so I will remember to get it ☺

7. Forts/Huts

Sunflower House (Books for Young Readers) by Eve Bunting (Author), Kathryn Hewitt (Illustrator)

A young boy plants the seeds in a large circle to grow a sunflower house. When the plants are tall enough, he invites his friends over to play in it. The text is written in rhyme.

Adult nonfiction books for gardening with children:

Gardening Wizardry for Kids by L. Patricia Kite and Yvette Santiago Banek

Roots, Shoots, Buckets & Boots: Gardening Together with Children by Sharon Lovejoy

This is the classic book on gardening with children. As you can tell from the title, Lovejoy has many fun and creative ideas about gardening.

A Child's Garden: 60 Ideas to Make Any Garden Come Alive for Children by Molly Dannenmaier

The hardcover copy I have says “Enchanting Outdoor Spaces for Children and Parents.” Enchanting is the right word. Mixed with informative text about how children play and how important it is for them to play outdoors, are photos of fairytale settings for children to play in. On pages 158-159 is a photo and list of the plants in the George Washington River farm alphabet garden.

binocular boy

Don’t you love it when you find a really great curriculum on-line for free? This weekend I found a terrific educational resource about birds. The author says it’s for elementary grades, but I think it could definitely be used at higher grades as well, with some modifications.

The guide is called “Desert Birding in Arizona, with Focus on Urban Birds" by Doris Evans, illustrated by Doris Evans and Kim Duffek. Although the book definitely emphasizes desert birds, many of the topics covered could be applied anywhere. For example, the first section answers the question, “Why study birds?” It’s relaxing, it gets us outdoors and birds can be observed year around. All those apply no matter where you are studying. The information in this curriculum guide would also be good to add to a unit on deserts.

The curriculum is available as a .pdf file. Go to the Arizona Fish and Wildlife, Focus:  WILD Arizona page, scroll all the way down to the bottom to “Additional Resources” and you’ll find a link to the Desert Birding in Arizona .pdf file. While you are visiting, you can see all the other educational materials available.

Hope you find it useful. Don’t forget to check page 35 for more information about rock doves (pigeons). 🙂