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Animals that construct homes use a variety of materials. Beavers build dams using sticks, stones, mud, and other resources. Birds use similar things to build their nests. Animals called silkworms take a different approach. They make their homes with stuff they spit out of their mouths. That worm spit is the material we call silk . A silkworm’s body works in a way that allows the food they eat to come out as silk.
When do silkworms spin silk?
Silkworms are really caterpillars . Like other caterpillars, they go through changes, or stages, all through their lives. During one of those stages, a silkworm will spin its silk and wrap its entire body into a temporary home called a cocoon . This silk wrapping works something like a sleeping bag. The animal stays inside its cocoon without eating or moving. While the silkworm rests, its body gradually changes into a fully formed silk moth. It develops wings and a different body. Then, it leaves its cocoon as a silk moth.
To get to that point, it must go through other changes. All silkworms begin their lives as eggs. Each adult female will lay hundreds of eggs on the leaves of mulberry trees. Each egg is no bigger than the dot at the end of this sentence. A few weeks later, the mulberry leaves will be filled with thousands upon thousands of newly hatched silkworms. Smaller than 1/8 of an inch (2 millimeters), they look like tiny, hairy, black ants.
When a silkworm gets old enough, it will spit out a single silk thread that sometimes reaches almost 3,000 feet (900 meters) long.
How do silkworms produce silk?
Before that can happen, a silkworm must get its body ready. It does that by eating. And eating. And eating. A little more than a month later its growth reaches about three inches (7 ½ centimeters). It looks like a creamy-white, soft, fat, caterpillar.
Silkworms grow as fast as they do by devouring mulberry leaves. They eat almost nonstop from the time they hatch until they are ready to begin spinning their cocoons.
Mulberry leaves contain a protein called fibroin (fi-bro in). A silkworm’s body must have enough of this special nutrient to produce all the silk it needs to spin its cocoon.
As a silkworm digests its food, the mulberry leaves break down and release their fibroin. This protein goes through two special silk-producing glands in the silkworm’s jaw called sericteries (si-rik-tuh-rees).
Changes take place inside the glands that turn the material into liquid silk. Silkworms also produce a protein called sericin (ser-uh-sin). It acts like glue that makes the silk stick together. A silkworm spins its cocoon from one long strand of liquid silk. It comes out of the animal’s mouth from something called a spinneret (spin-uh-ret). This body part is located at the end of the sericteries. Although a silkworm releases liquid silk, the material turns into a solid thread when it makes contact with air.
How do silkworms construct cocoons?
A silkworm makes its cocoon by swinging its head around in a way that looks like a sideways number eight. This motion allows the animal to wrap its entire body inside the cocoon. It will use every bit of silk in its body and can take up to three days to finish the cocoon.
Now, it is called a pupa . The cocoon protects the pupa from predators and changes in weather. It takes about seven to fourteen days for a pupa to change into a silk moth. Then, it releases a liquid that makes a hole in the cocoon and allows the silk moth to break free.
Silk moths do not eat. So, they only live a few days. However, during that time they carry out one of nature’s most important jobs. Male and female silk moths mate and produce the eggs that will create the next generation of silkworms. These new babies will repeat the process. They and all the generations that come after them will continue using their worm spit so that their cocoons can make new life possible.
The lifecycle of a silkworm
The lifecycle lasts about between six and eight weeks
Eggs hatch in about 7-14 days at temperatures ranging from 75°-82°Farenheit (24°-28° Celsius).
About 31 days in the caterpillar stage
About 10 days as a pupa inside its cocoon
About 5 days as an adult silk moth
Fun facts
Silkworms grow as fast as they do by devouring mulberry leaves. They eat almost nonstop from the time they hatch until they are ready to begin spinning their cocoons.
When a silkworm gets old enough, it will spit out a single silk thread that sometimes reaches almost 3,000 feet (900 meters) long.
Flesch Kincaid Grade Level 5.7
Flesch Kincaid Reading Ease 78
Glossary
Caterpillar: A stage of insect development between the egg and the pupa. It is sometimes called a larva
Cocoon: A covering made from silky threads produced by some animals to protect themselves or their eggs
Fibroin: A protein made up of raw silk fiber
Silkworm: A caterpillar that spins a cocoon of silk thread
Pupa: the stage of an insect between the larva and the adult when it encloses itself in a cocoon
Sericin: A gummy protein that binds the two strands of silk together
Sericteries: the silk producing glands of a caterpillar and or other insect larva.
Silk: A soft, shiny material made from threads produced by silkworms.
Spinneret: a body part used for producing silk threads from the liquid in silk glands
References
Sahay, Ankita. (Last Modified 2022, May 18). Life History of Silk Moth: Introduction, Various Stages, Processing Of Silk. Retrieved May 22, 2022, from https://www.embibe.com/exams/life-history-of-silk-moth/
Collegedunia Team, Content Curator. (Updated 2022, April 4). Silkworm: Life Cycle Of Silkworm And Silk Production. Retrieved May 15, 2022, from https://collegedunia.com/exams/silkworm-life-cycle-of-silkworm-and-silk-production-articleid-1776
van den Burg, Erwin. (2021, August 16). Existence Cycle Of The Silkworm. Retrieved May 20, 2022, from https://sciencebriefss.com/nature/existence-cycle-of-the-silkworm/
Abbe, Olivia. (2020, August 11). How Is Cocoon Formed In Silkworms? Retrieved May 20, 2022, from https://nykdaily.com/2020/08/how-is-cocoon-formed-in-silkworms/
Yan, Daphne. (2016 October 20). Life Cycle Of The Silkworms. Retrieved May 19, 2022, from https://risingstarmagazine.com/life-cycle-silkworms/
Zuch, Ariel. (2015 June 11). Dissect A Silkworm Cocoon. Retrieved June 1, 2022, from https://www.sciencefriday.com/educational-resources/dissect-a-silkworm-cocoon/#:~:text=After%20constructing%20its%20cocoon%2C%20the%20silkworm%20caterpillar%20is,is%20left%20in%20the%20bottom%20of%20the%20cocoon
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