Have you ever seen a caterpillar transform into a beautiful butterfly? There are few transformations in nature as miraculous and fascinating as the process of becoming a butterfly.

Butterflies go through a life cycle that involves several stages: egg, larva, pupa, and adult. The metamorphosis from a caterpillar into a butterfly occurs during the pupa stage. During this stage, the caterpillar’s old body dies and a new body forms inside a protective shell known as a chrysalis.

Moth caterpillars and many other insect larvae spin silk coverings for the chrysalis. These silk casings are called cocoons. Cocoons can be soft or hard, solid or web-like and any of several different colors or even see-through.

Cocoons provide camouflage and additional protection for the chrysalis. Many moth caterpillars will spin their cocoons in concealed locations, such as the underside of leaves, at the base of a tree, or hanging from a small branch.

While some people think of cocoons as a resting place, there’s no resting going on inside the cocoon! To the contrary, there’s a lot of activity. Inside the cocoon and the chrysalis, the caterpillar is transforming into a new creature. This requires that the old caterpillar body be broken down and turned into something new. Think of it as insect recycling!

Inside a chrysalis, a caterpillar’s body digests itself from the inside out. The same juices it used to digest food as a larva it now uses to break down its own body!

The fluid breaks down the old caterpillar body into cells called imaginal cells. Imaginal cells are undifferentiated cells, which means they can become any type of cell. Many of these imaginal cells are used to form the new body.

The process of transformation within the chrysalis is known as holometabolism. Although it varies by species, the whole process usually takes about two weeks. In some species, though, the process can take months if they stay inside the chrysalis to survive cold winter weather.

Insects that spin cocoons must eventually escape from them to complete their transformation. Some escape by cutting their way out from the inside. Others may secrete fluids that soften the cocoon and make it easier to escape.

26 Join the Discussion

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    • We’re so happy that you enjoyed today’s Wonder, Kate! The life within the cocoon is certainly fascinating! Science rocks! :)

  1. Your wonder today is a great explanation of one of God’s beautiful creations! Butterflies are so fun to watch as they flutter from plant to plant in the garden.

    • Hey Tommy, we’re thrilled to know that you’ve been WONDERing with us today! Thanks for sharing your comment, we really appreciate it! Have a SUPER day! :)

  2. I was wrong. But a question arises… How is it that a cocoon can hold a Caterpillar on a branch when it’s so light?
    I think tomorrow’s WONDER will be about Hawaii, Florida, Fiji, or London.

    • Hey there, Emily, we’re so glad you are here today! Cocoons are strong enough to keep the caterpillar safe while it changes and grows. Isn’t it incredible to learn all about the stages of life before a butterfly can soar in the sky? Thank you for sharing your far-away Wonder guesses- nice work! :)

  3. Can you make a blog about how you make paper? Or a blog about babies or something like that? I like this blog and keep doing it.

    • Thanks so much, Beau! We Wonder if you have ever seen a cocoon in your backyard… or perhaps you’ve seen a butterfly? :)

  4. Dear Wonderopolis, In my second grade class are studying insects and we each have 2 baby caterpillars. My two are named Jack and Rose. My teacher had four kids last year whose caterpillars died. I hope that mine do not die. My class has them until they turn into butterflies. I learned that a butterfly has to expand its wings before she/he can fly! Your Friend, Emma

    • Hey there, Emma, we hope Jack and Rose stay safe and sound in your class today! It sounds like you’re in for a real science treat! Thanks for telling us all about your cool science class! :)

  5. About 4 years ago, in the summer, My dad and I raised about 37 caterpillers. Only one didnt survive and I cried! :`(

    Oh well. It was a fun experience!

    • Hey there, Rainbow Dash! Thanks for telling us all about your caterpillar adventure with your dad. We’re sorry to hear that none of the caterpillars survived, but we are so happy that you learned all about their lives while you cared for them. Keep up the awesome SCIENCE work! :)

    • HOORAY! Thank you for sharing your awesome comment with us today, Wonder Friends in Mr. Johnson’s Class! It sounds like you have learned something new about the cool changes that take place inside a cocoon! Thanks for visiting us to Wonder! :)

  6. This wonder is awesome! When I was in 2nd grade our teacher kept caterpillars in the classroom. We got to see them transform into butterflies! We also got to see silk worms turn into moths in 2nd grade also! The caterpillar’s cocoon is actually called a chysallis. The silkworm’s cocoon is called a cocoon. :lol:

    • What an awesome connection to our growing Wonder, Julie! Nice work! It sounds like you’ve seen this Wonder up close and personal in 2nd grade- how neat! We loved learning about that cool experience in your classroom and we appreciate all the WONDERful facts you have shared today! If you could be any type of insect, what would it be? :)

    • Hi Shaan! We agree! The Wonder says that a caterpillar forms a cacoon, transforms itself, and becomes a butterfly! Thanks for WONDERing with us! :)

    • Hi Wonder Friend! We’re so glad we could help! Is there a favorite butterfly that you like? Thanks for WONDERing! :)

  7. Student question: “Is the butterfly in the cocoon or is he out?”

    Student question: “What kind of butterfly is in the video?”

    curious, weird, cool, awesome

    • Great questions from Mrs. Gill’s students! The butterfly is a butterfly once it leaves the cocoon. The butterfly in the video is a black swallowtail butterfly. Thanks for WONDERing with us today, Wonder Friends! :-)

    • Those are great questions, Shane! We’re not sure. We hope you’ll investigate further and share with us what you learn! :)

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Have you ever wondered…

  • What goes on inside a cocoon?
  • What is a cocoon made of?
  • Which insects make cocoons?

Wonder Gallery

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Try It Out

Grab a friend or family member and explore one or more of the transformational activities below to help extend your learning about butterflies:

  • Feeling crafty? Try out this fun arts and crafts project that helps you turn what you learned today into an artistic outlet for your creativity!
  • Ever feel like crawling up in your own life-size cocoon? On cool nights, it can be fun to wrap yourself in several blankets when it’s time for bed. It can also be fun to pretend that years and years have passed while you’ve been resting in your cocoon. Grab a friend or family member and some sleeping bags or blankets. Have them help you build your own personal cocoon. Crawl inside with a notebook and a pen and pretend that you’re in the cocoon for about five years. Take some notes as you think about these questions:
    • What will the world be like when you come out of your cocoon?
    • What changes have taken place while you’ve been resting?
    • What’s the first thing you want to do after a five-year nap?

Share your thoughts with your friends and family members. What do they think the world will be like five years from now? Would they want to take a nap and wake up five years later? Why or why not? What would you miss the most during that time? Have fun using your imagination in your homemade cocoon!

  • Up for a challenge? Do your own Internet research to learn how the transformational processes that frogs and toads go through compare to what you know about the metamorphosis of the butterfly. (This Wonder of the Day will get you started.) How are they similar? How are they different? Make a chart comparing the two processes. If you can, turn your work into a multimedia presentation, complete with images and video that you can share with friends, family members, and classmates. Have fun learning about some of nature’s other miraculous processes!

Still Wondering

In National Geographic Education’s Monarch Butterfly Life Cycle and Migration activity, children watch a time-lapse video of the monarch butterfly life cycle. They illustrate and label the life cycle and then research and take notes on survival techniques and preparation for migration at each stage.

Wonder What’s Next?

Tomorrow’s Wonder of the Day takes a trip to one of our favorite places!

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