Study Life Cycles with Butterflies
By Lynne Kepler

Kids can use this butterfly unit to investigate changes in their own lives

Nearly a dozen monarch caterpillars occupy the small aquarium each September. As each new school year begins, my three children gather caterpillars from the leaves of the milkweed plants that grow along the roadside, make a home for them, and watch them grow. Every year, my kids are astounded by the incredible change from caterpillar to striking, black-and-orange butterfly. And every year, I'm awed by the change and growth in my kids. Here you'll find fresh, hands-on investigations that compare butterfly and human life cycles –– and help you connect math and science, too.

HANDS-ON SCIENCE: FROM CATERPILLARS TO BUTTERFLIES

Concepts: Insects undergo dramatic changes throughout their life cycle. All living things change during their lifetimes.

Skills: observing, predicting, measuring, communicating, comparing, and contrasting.

Vocabulary

caterpillar: the larval stage of a butterfly or moth

chrysalis: the hard shell covering the pupa; shaped like an upside down teardrop

larva: the second stage of metamorphosis, during which an insect is wormlike and has new wings

pupa: the third stage of metamorphosis; encased by a chrysalis

metamorphosis: a series of developmental stages often marked by body changes

Finding the Caterpillars

The best way to find caterpillars is to locate their food source. Monarch caterpillars feed only on milkweed. Several species of this common wildflower grow throughout the United States. To find the yellow-black-and-white-striped caterpillars, lift the plant's leaves. Gently pull the caterpillars off and transport them in a ventilated jar to school. If you'd rather purchase caterpillars, see the resource box on the next page for ordering information.

Making the Habitats

To care for the caterpillars, you will need a container that allows them to get air and to move around. A small aquarium with a screen lid works well. If you wish to have groups of students make their own caterpillar habitats, here is an easy way to do it.
  1. For each group of students, gather two plastic 2-liter soda bottles (emptied and cleaned) and a small piece of window screening.

  2. Cut the top off around the shoulder of one of the bottles, as shown. (If working with younger students, cut the bottles for them.)

  3. To make a lid for the habitat, set the base of the second bottle in warm water and then pull it off. Cut a piece of wire screen to fit inside the lid. Tape the screen in place. This will give the caterpillars a place to attach themselves and keep them from escaping.

  4. Add the caterpillars and a few fresh, moist leaves –– the kind your caterpillar eats — to the habitat. (If you order a butterfly kit, you'll get the food with it.) Replace the food supply as needed.

Activities Kids Love

It takes about two weeks for a caterpillar to become a chrysalis. Here are some investigations your students can do as you watch the caterpillars grow.
  • Make a bar graph. Ask students: How much do the caterpillars grow? Do they all grow at the same rate? To find out, students can measure the caterpillars using a piece of yarn. Cut the yarn to match the length of each caterpillar, then tape the yarn pieces to a sheet of 9-by-12-inch construction paper. Record the date on the paper next to the pieces of yarn. Students can do this every few days, creating a bar graph of the caterpillars' growth.

  • Make a line graph. Invite older students to use rulers to measure the caterpillars' growth daily and record their data in a notebook. Students can determine the average daily growth rate of their caterpillars. They may also make a line graph noting any growth spurts or plateaus. Do the students notice any patterns?

  • Keep daily diaries. How does a caterpillar change? Students can keep daily journals, describing in words and pictures the caterpillars' changes. Once the caterpillars have become chrysalises, invite students to make a sketch in their journals of what they think the butterfly will look like, then make another sketch when the butterfly emerges. After the butterflies have emerged, move them to an aquarium to observe for a day or two before releasing them. Place a wet sponge in a dish so they have water to drink.

Extension Activity: Circle of Life

Discuss with students how the butterfly develops through four stages of metamorphosis — egg, larva (caterpillar), pupa (chrysalis), and adult (butterfly). The adult barely resembles the larval stage in appearance or behavior. This is known as a complete metamorphosis.

Invite students to compare the butterflies' growth and changes with their own growth and development. Ask them to bring in pictures of themselves as infants and toddlers. Using these photos and their caterpillar charts and diaries, students can create two circles of life — one for the butterfly and one for themselves. To make a circle of life, each student will need two sheets of white construction paper, a file folder, and a brass paper fastener. Here's how to assemble the circles.

  1. Glue two sheets of paper together along one edge. Mark and cut out a 1-inch window from the top sheet.

  2. Cut out a circle from the file folder. The diameter of the circle should just about match the width of the paper. Poke a small hole through the center of the circle.

  3. Have students paste their photos or caterpillar/butterfly drawings onto the circle, as shown.

  4. Insert the circle between the sheets of paper, leaving one edge of the circle — which will now function as the wheel — exposed. Adjust so that each picture shows up through the window when you turn the wheel.

  5. Using the paper fastener, fasten together the wheel and the paper, then glue the paper edges, leaving only the section with the wheel edge open.

  6. Students can share their circles with each other, narrating the changes seen through the window.

  7. Students can also use photographs of parents, grandparents, and so on to create more life-cycle wheels. Invite students to brainstorm what other kinds of life cycles they can depict.

Resources

Books

Butterfly Story by Anca Hariton (Dutton, 1995)

Life of the Butterfly by Heiderose and Andreas Fischer-Nagel (Carolrhoda, 1995)

The Butterfly Alphabet Book by Brian Cassle and Jerry Pallotta, illustrated by Mark Astrella (Charlesbridge, 1995)

The Moon of the Monarch Butterflies by Jean Craighead George (HarperCollins, 1993)

Butterflies Abound! A Whole Language Resource Guide for K-4 by Seddon Beaty (Addison-Wesley, 1993)

Video

Geo Kids: Tadpoles, Dragonflies, and the Caterpillar's Big Change (National Geographic Society). For information or to order, call (800) 368-2728.

Software

Animals and How They Grow (for Macintosh) is a CD-ROM package for grades K-2. Use it to compare insect and other animal life cycles. (National Geographic Society, [800] 368-2728).

Butterfly Suppliers

The following companies will ship painted lady caterpillars directly to your school. They also have catalogs of other butterfly-related materials.

Insect Lore, P.O. Box 1535, Shafter, CA 93263; (800) LIVE-BUG

Let's Get Growing, 1900 Commercial Way, Santa Cruz, CA 95065; (800) 408-1868


Lynn Kepler (Science), a science writer and consultant based in Pennsylvania, also works in the classroom as an elementary-school teacher.

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