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Essential Science for Teachers: Life Science

Bottle Biology | Bottle Basics Brassica & Butterfly System

Brassica & Butterfly System

The Brassica & Butterfly System (see building instructions below) will allow you to observe an entire plant life cycle along with an entire animal life cycle over a relatively short time period. The plant, Brassica rapa, is a variety that belongs to the mustard family. It has been selectively bred for a rapid life cycle: from seed to seed in about 30 days. These plants have been nicknamed “Fast Plants.” The animal is Pieris rapae, an insect known as the cabbage white butterfly. Pieris also has a life cycle that occurs over about 30 days.

The connection between the two involves feeding and reproduction. Pieris larvae are particularly fond of eating Brassica leaves, while Pieris adults feed on the nectar in Brassica flowers. As the butterflies move from flower to flower, they pollinate the Brassica plants. In addition, Pieris adults are attracted to Brassica leaves for egg-laying.

There are many activities that can be done with BrassicaPieris, or both. Life Science has suggested a few that can help you understand plant and animal life cycles better–and that can be used with great success in K-6 classrooms. The “Brassica & Butterfly Life Cycles” activity follows the progress of Brassica from seed to seed as it interconnects with the life cycle of Pieris from egg to egg. “To Bee or Not to Bee” is an activity you can do to see what happens to Brassica flowers that are pollinated and those that are not. The “Salad Bar” activity tests the feeding preferences of Pieris larvae; and in “How Sweet It Is,” different sugar concentrations are used to see the effect on adult Pieris feeding. Finally, with the “Mother Knows Best” activity, you can see on what types of plants Pieris prefers to lay eggs.

You can follow along online and “Track Our Progress” with these activities: Brassica & Butterfly Life Cycles,” “The Salad Bar,” and “Mother Knows Best.”

For more information and activities for this system, visit the Fast Plants Web site at

Build the System: Components

Brassica Components

Your Brassica plants will need a place to grow undisturbed from seed to flower. To do this, you’ll need the following:

  • Bottle Growing System – to sprout and grow the plants
  • Light House – to provide continuous high-quality light and a source of heat

Pieris Components

Pieris will need different components for different stages in its life cycle:

  • Brassica Nursery – for hatching eggs, and for feeding the first few larval stages
  • Brassica Barn – for feeding the larvae until they become pupae, and for housing the pupae
  • Bottle Growing System and Light House (both from above) – for housing and feeding the adult butterflies, and to provide an environment for egg-laying

Activity Accessories

Depending on the activities you choose to do, you may need one or more of the following:

  • Bee Stick – for the “To Bee or Not to Bee” activity
  • Film Can Sugar Feeder – for the “How Sweet It Is” activity
  • Film Can Ovipositron – for the “Mother Knows Best” activity

Build the System: Bottle Growing System


Materials Needed

For Building

  • One one-liter plastic bottle (provides a deep base unit and top unit)
  • One bottle cap
  • One 20 cm length of nylon craft cord (for wick)
  • China or non-permanent marker (for making marks)
  • Safety razor or utility knife (for starting bottle cuts)
  • Scissors (for finishing bottle cuts)
  • Soldering iron or drill (for making wick hole in bottle cap)

For Stocking and Maintaining

  • One package of Fast Plant (Brassica rapa) seeds (can be ordered from Carolina Biological Supply Company (1-800–334–5551) or
  • Potting soil mix (Jiffy-Mix™, Scott’s Redi-Earth™, or 1:1 peat moss and vermiculite)
  • Fertilizer solution (Peters Professional TM Fertilizer™ or Miracle Gro™)

Building Instructions

  1. Following the instructions for making cuts in Bottle Basics, make a top unit and a deep base. Note: You may wish to make two to three Bottle Growing Systems at the same time because they are used in many systems.
  2. Melt or drill a hole in the bottle cap and screw onto the top unit.
  3. Insert the wick through the hole in bottle cap with approximately 10 cm on either side.
  4. Invert the top unit over the deep base.

Stocking Instructions

  1. Moisten the potting mix.
  2. Fill the top unit with potting mix to about 5cm from the rim.
  3. Apply water gently to the mix until it is dripping from the wick below.
  4. Add more potting mix until settled but being careful not to pack heavily.
  5. Distribute 20–25 seeds onto the potting mix.
  6. Cover the seeds lightly with a thin layer of potting mix.
  7. Fill the deep base about 3/4 full with fertilizer solution (follow instructions on fertilizer container).
  8. Place inside a Light House and follow instructions for maintaining.

Maintenance Instructions

  1. Keep the deep base supplied with fertilizer solution.
  2. Thin seedlings so that each is at least .5 cm from the others.

Build the System: Light House


Materials Needed

For Building

  • One copy machine paper box (approximately 17″ x 12″)
  • One dessert size plastic plate (to suspend light source)
  • One Gro-lite (light source)
  • One light socket with extension cord (to connect light source to power)
  • Nylon mesh (for ventilation windows and front screen)
  • Heavy duty aluminum foil (to line box and make the front panel)
  • Velcro strips or tabs (to secure front panel to box)
  • Small binder clips (to secure front screen to box)
  • Utility knife
  • Scissors
  • Household glue
  • Duct tape

Building Instructions

Box unit:

  1. Cut 5 X 20 cm windows in the sides and back of the box near the top center.
  2. Cover the windows with nylon mesh using duct tape to secure.
  3. Line the box with shiny side of the aluminum foil facing in using a glue stick to secure it.
  4. Cut a hole in the top center of the box large enough to insert the base of the light.
  5. Cut a hole of the same size in the center of the plastic plate and trim the raised edges to make a flat disk.
  6. Place the disk on top of the box, over the light socket hole.
  7. Insert the light from inside of the box through the hole and the disk.
  8. Secure the light to the light socket and plug in the extension cord.

Front panel: (Will be used when growing plants in Light House)

  1. Measure the side and top (length and width) dimensions of the box. Add 5 cm to the side measurement (for folding over top of box).
  2. Cut the aluminum foil panel to the above measurements.
  3. Fold the duct tape over each edge of the panel to add strength.
  4. Secure three pieces of one side of the Velcro strip to the top edge of the panel.
  5. Secure three pieces of the other side of the Velcro strip to the top outer edge of the box (match placement with the strips on the panel).
  6. Suspend the panel by folding the top edge over the top of the box so it is attached with Velcro.

Front screen: (will be used when housing butterflies in Light House)

  1. Cut the screen using the same measurements for the front panel (above).
  2. Use binder clips to secure the front screen to the Light House.

Build the System: Brassica Nursery


Materials Needed and Instructions

For Building, Stocking, and Maintaining

See Bottle Growing System. The only difference involves the seeds used and the addition of Pieris eggs.

The Brassica Nursery uses a variety of seeds to grow different plants to feed the larvae. Turnip, radish, and lettuce seeds can be purchased from a garden store and mixed together. Fast Plant seeds can also be used in the mix. The seeds should be planted about five days before the eggs arrive.

Pieris eggs can be purchased from Carolina Biological Supply Company (1-800-334-5551 or The eggs should be ordered to arrive about 5 days after the seed mix has been planted, so that the larvae will have something to feed on. When the eggs arrive, they will be on a strip of wax paper in a small plastic vial. With tweezers, remove the wax strip carefully and place it egg side down on the plant seedlings. Do not touch the eggs!

Note: During larval stages, Pieris should be kept away from the Brassica being grown in the Light House System. This will prevent them from eating plants that need to grow to the flowering stage.

Build the System: Brassica Barn


Materials Needed

For Building

  • One 16 oz plastic deli container with lid (will support 10-15 larvae)
  • Five heavy duty toothpicks (for skewering the Brussels sprouts)
  • One paper towel (for the bottom of the container)
  • One nail poke, push pin, or soldering iron (for poking holes)

For Stocking and Maintaining

  • Five Brussels sprouts with top leaf removed
  • Extra paper towels

Building, Stocking, and Maintenance Instructions

  1. Poke five holes for toothpicks at “N, E, S, W” and center locations on the deli container lid.
  2. Poke small air holes in several areas elsewhere on the lid.
  3. Skewer the Brussels sprouts with the toothpicks.
  4. Insert toothpicks through the bottom side of the lid.
  5. Layer the bottom of the container with paper towel.
  6. Place the lid with the Brussels sprouts on top of the deli container.
  7. Add 2-3 larvae from the Brassica nursery to each Brussels sprout. (about Day 10)
  8. Keep Brussels sprouts free of “frass” (larval droppings).
  9. Remove and replace the paper towel every couple of days.

Build the System: Bee Stick


The bee stick is used for pollinating Brassica flowers. The bee stick requires a dead bee mounted at the tip of a toothpick. You can purchase dead bees from Carolina Biological Supply Company (1-800–334–5551) or Alternatively, you can find your own dead bee (or other flower-feeding insect), or use a fine paint brush.

Build the System: Film Can Sugar Feeder


Materials Needed

For Building and Stocking

  • Four clear plastic film canisters (to hold sugar solutions)
  • Four 10 cm lengths of nylon craft cord or felt (for wicks)
  • Sugar

Building and Stocking Instructions

  1. Fold each length of nylon craft cord in half.
  2. Insert one length into each film canister, loop end down.
  3. Fill each canister about 3/4 full with water.
  4. Leave one canister with just water.
  5. To the remaining three canisters, add 1 tsp., 2 tsp., and 3 tsps. of sugar respectively.
  6. Place into a Light House with adult butterflies when ready to do feeding activities.

Build the System: Film Can Ovipositron


Materials Needed

For Building and Stocking

  • Six clear plastic film canisters with lids (to act as bases to hold leaves)
  • Six different types of plant leaves (Fast Plant, cabbage, and non- Brassicas like lettuce and spinach)
  • Scissors
  • Double-sided transparent tape
  • Wax paper

Building, Stocking, and Maintenance Instructions

  1. Cut circles roughly the same size as the film canister lids from each leaf.
  2. Using double-sided tape, attach one leaf to each lid.
  3. Cut six 1cm X 10cm strips of wax paper.
  4. Using pieces of double-sided tape, attach the wax paper strips to the film canister by encircling the top. Be careful not to leave the tape exposed, as the butterflies may get caught on it.
  5. Place into a Light House with adult butterflies when ready to do egg-laying activities.


Now that you’ve built the components you need for the Brassica & Butterfly system, try these activities to further your understanding of this system. First, read the instructions and perform the activity. Then, for selected activities, view an example system in track our progress.

  • Brassica & Butterfly Life Cycles… What happens during a typical plant life cycle? What about the life cycle of a familiar insect? [track our progress]
  • To Bee or Not to Bee… What is the role of pollination in a plant life cycle?
  • The Salad Bar… Are Pieris larvae picky eaters? [track our progress]
  • How Sweet It Is… Nectar is sweet, but is it possible that varying levels of sweetness might have an impact on Pieris feeding?
  • Mother Knows Best… Do female adult Pieris butterflies prefer to lay their eggs on specific plant types? [track our progress]

Brassica & Butterfly Life Cycles

What happens during a typical plant life cycle? What about the life cycle of a familiar insect, like a butterfly? This activity explores the life cycles of Fast Plants, or Brassica rapa, and Pieris rapae, the cabbage white butterfly.

Materials Needed


To prepare

  • Order your Fast Plants seeds and butterfly eggs, and buy seeds for the Brassica Nursery from a local garden shop (radish, turnip, and/or mustard seeds). NOTE: You’ll need to plant the seeds about five days before the butterfly eggs arrive, so time their arrival accordingly.
  • Before the Fast Plant seeds arrive, build the Bottle Growing System, Light House, Brassica Nursery, and Brassica Barn.
  • When they arrive, plant the Fast Plant seeds in the Bottle Growing System and place it in the Light House.
  • On the same day or a few days earlier, plant the seed mix in the Brassica Nursery and place it in the Light House.

When the butterfly eggs arrive

During the study period

Both life cycles will take about 30–40 days to complete. During this time, make observations every 2–3 days. Use your Brassica & Butterfly Data Sheets (PDF) to record what you observe and answer questions.

Visit for in-depth information on the Brassica and the butterfly.

Activity Questions

Brassica questions

  • How does a seed germinate?
  • What environmental conditions do seeds need for germination?
  • Where do new plant parts (roots, stems, leaves, flowers, and pods) develop?
  • How do plants get the carbohydrates (sugar) they need for energy to grow?
  • What is the purpose of each structure (roots, stems, leaves, flowers, and pods)?
  • Why are insects attracted to the flowers?
  • Do all seeds on a plant have the same mother? The same father? Explain.
  • Are the seeds alive? Justify your answer.

Butterfly questions

  • How do the larvae hatch from the eggs?
  • What clues indicate that larvae are present, even if you can’t locate them?
  • What do the larvae eat?
  • Where would you expect to find larvae?
  • What do the larvae expel?
  • Each larva has an exoskeleton. What is the function of the exoskeleton?
  • How do the larvae grow larger? What happens to the exoskeleton?
  • How do the larvae become butterflies?
  • What indicates that a larva is ready to form a chrysalis?
  • What indicates that a butterfly is ready to emerge from a chrysalis?
  • Where do female butterflies tend to lay their eggs? Why?
  • What is the difference between the food for the larvae and the butterflies?
  • What food needs to be present for another generation of butterflies to survive?

Brassica & Butterfly questions

  • How does the Brassica depend on the butterfly?
  • How does the butterfly depend on the Brassica?

TRACK OUR PROGRESS for the Brassica & Butterfly Life Cycles Activity

To Bee or Not to Bee

Fast Plants are pollinated by many insects, including Pieris rapae and bees. What is the role of pollination in a plant life cycle? What happens if flowers aren’t pollinated? Try this with the plants being used in the Brassica & Butterfly Life Cycles activity to find out!

Materials Needed

  • Fast Plants in Bottle Growing System
  • Bee stick(s)


  • Just before flowers begin to open (about Day 12), use small squares of plastic wrap and twist ties to loosely enclose 3–4 groups of flowers on different Brassica plants. Do not disturb these flowers any further.
  • Using your bee stick, transfer pollen gently from flowers on one plant to flowers on another. Do this with as many flowers as you can.
  • Continue to observe each plant until the end of its life cycle (about Day 40).
  • Describe what you see in both groups of flowers, and make a sampling of sketches as you do.

Activity Questions

  • What is the role of a flower in a plant life cycle?
  • What parts of the flower are most important to completing the life cycle? Make a sketch of these parts and their relationship to one another.
  • Describe specifically what you did to pollinate the flowers.
  • Describe what happens to the flowers after you pollinate.
  • What forms from the flowers?
  • Make a sketch to compare the differences between what happens to flowers that were pollinated and those that were not.
  • What can you conclude about the importance of insects, like bees, to the pollination of Fast Plants?
  • In the absence of insects, what else might help ensure pollination?


The Salad Bar

Are Pieris larvae picky eaters? Find out by providing them with their very own salad bar.

Materials Needed

  • Three plastic plates
  • Six leaves for feeding trials*
  • Three Pieris larvae from the Brassica Barn

* Select from members of the Brassica family (cabbage, broccoli, turnips, pak choi, kale, mustard greens, etc.) and non-Brassicas (lettuce, beet leaves, celery leaves, carrot leaves, spinach, etc.).


  • Make three dime-sized portions from each leaf. You can also use a hole punch to make more precise portions.
  • Place one portion from each leaf in a circular pattern near the outside of one plate. Repeat this for the two remaining plates.
  • Gently remove three Pieris larvae from the Brassica Barn, and place one in the center of each dish. You can use more larvae if you wish.
  • Observe and describe what happens. Record results at 2 hours, 4 hours, and 24 hours.

Activity Questions

  • How did the larva(e) behave when introduced into the container?
  • Which plants did the larvae eat?
  • Compare how much was eaten from each leaf.
  • What can you conclude about the feeding preferences of Pieris larvae?

TRACK OUR PROGRESS for The Salad Bar Activity

How Sweet It Is

Adult Pieris feed upon the nectar of Brassica plants. Nectar is sweet, but is it possible that varying levels of sweetness might have an impact on Pieris feeding?

Materials Needed

    • Four film Can Sugar Feeders, prepared as described

Adult Pieris feed upon the nectar of Brassica plants. Nectar is sweet, but is it possible that varying levels of sweetness might have an impact on Pieris feeding?

Materials Needed

      • Four Film-Can Sugar Feeders, prepared as described
      • Adult Pieris butterflies in a Light House


      • Place the Sugar Feeders into a Light House containing adult Pieris butterflies.
      • Observe the feeding behavior of the butterflies.
      • For each feeder, keep track of how many butterflies feed during a specific time period.
      • Keep track of how long the butterflies spend feeding at each Feeder.
      • Leave the Feeders in the Light House for a 48-hour period. At the end of this period, compare how much sugar solution is left in each.

Activity Questions

      • How did the butterflies behave when introduced to the Feeders?
      • How would you describe the way that the butterflies “tasted” each solution?
      • Which solutions, if any, were preferred by Pieris? What’s your evidence?


Mother Knows Best

Do female adult Pieris butterflies prefer to lay their eggs on specific plant types? Find out by providing them with different types of plant leaves.

Materials Needed

  • 4-6 Film-Can Ovipositrons, prepared as described
  • Adult Pieris butterflies in a Light House


  • Place the Ovipositrons into a Light House containing adult Pieris butterflies.
  • Observe the egg-laying behavior of the female butterflies.
  • For each Ovipositron, over a specific time period, keep track of how many butterflies land and fly away vs. how many land and lay eggs.
  • Leave the Ovipositrons in the Light House, and observe and record comparative results at 2 hours, 4 hours, 24 hours, and 48 hours.

Activity Questions

  • How did the butterflies behave when introduced to the Ovipositrons?
  • How would you describe the process of egg-laying?
  • What do you think the butterflies do to select a plant for egg-laying? What’s your evidence?
  • What plants, if any, seem to be preferred for Pieris egg-laying?
  • What are the consequences of egg-laying to a plant?

TRACK OUR PROGRESS for the Mother Knows Best Activity

Track Our Progress

Get a glimpse of our system at various points in selected activites. Remember that every system is unique: don’t expect yours to look exactly like ours!

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Essential Science for Teachers: Life Science


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