LESSON

6 The Cabbage White— From Egg to Butterfly Inquiries Periods

3 3–5 STUDENT OBJECTIVES Explain the meaning of the word “Lepidoptera,” the order of insects to which butterflies and moths belong.

CONCEPTS Butterflies belong to a class of arthropods called insects.

Explain the life cycle stages of the cabbage white butterfly.

OVERVIEW In this lesson, students begin a series of three inquiries into Pieris rapae, the cabbage white butterfly. To accommodate the variability of the length of its life cycle stages, the inquiries in this lesson are not conducted in direct succession. Instead, they are spaced out over approximately 1 month. In the first inquiry, students use a microscope to observe, draw, and measure an egg and a newly hatched larva of the cabbage white butterfly. They repeat the measurement of the body length of the larva every 3 days for 3 weeks to track its growth. They use this information to update their cabbage white organism photo cards. In about 2 weeks, they perform Inquiry 6.2, in which they investigate the food preferences of a cabbage white larva. After observing the development of the cabbage white for almost a month, students conduct Inquiry 6.3 to determine whether the adult cabbage white butterfly is attracted to one color of food over another.

SAMPLE

Butterflies undergo four life stages: egg, larva, pupa, and adult.

Measure the length of an egg and the length of the body of a newly hatched cabbage white butterfly larva.

The process by which a butterfly develops through its four life stages is called metamorphosis.

Measure and record the body length of a cabbage white larva every 3 days for 3 weeks.

Many organisms eat only very specific food types.

Observe the food preferences of a cabbage white butterfly larva.

Narrow food preferences can limit habitat options for an organism. The excrement of animals often reveals information about the foods they eat.

Determine whether adult cabbage whites prefer one color of food over another. Investigate the basic anatomy of an adult cabbage white butterfly. Update the organism photo card for the cabbage white butterfly.

BACKGROUND This lesson differs from the other lessons in this module in that the three inquiries are conducted over a 1-month period. After completing Inquiry 6.1, students move on to Lesson 7. They continue to move forward through the lessons, returning to Inquiries 6.2 and 6.3 as dictated by the development of the larvae.

Inquiry 6.1 Inquiry 6.1 is conducted during the first class period of Lesson 6. Students sketch an egg and a newly hatched larva of a cabbage white butterfly while observing them through a microscope. In addition, they begin a 3-week activity in

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which they measure a larva’s length every 3 days. They use this information to determine during which time period the greatest amount of growth occurs. Reading Selection An introductory reader, “Introducing the Cabbage White Butterfly,” provides students with sufficient background information to begin their investigation.

Inquiry 6.2 Inquiry 6.2 should be conducted when the larvae have reached the fourth instar stage. (Detailed information on the cabbage white’s larval stages is included in this Background.) Since larval development may vary somewhat because of external factors such as room temperature, you must decide when to fit this inquiry into the module. Inquiry Master 6.1: Cabbage White Butterfly—Inquiry, Care, Preparation, and Maintenance Calendar suggests an approximate time to introduce this inquiry.

Inquiry 6.3 Students must conduct Inquiry 6.3 a few days after the adult butterflies have emerged from their chrysalises and are feeding regularly. Look at your maintenance calendar (Inquiry Master 6.1A) for the best time to conduct this inquiry. A few days before doing so, you will need to put a sheet or two of white copy paper on the floor of the butterfly cage. As the butterflies feed on the different colors of sugar-honey-water mixture in the feeders, they will leave different colored droppings on the paper. Time will not permit you to prepare enough of these spot-laden sheets for each group in all of your classes. For that reason, color photocopies of a sheet taken from the bottom of a butterfly cage are supplied in your materials kit. By using the photocopied sheets, you also eliminate the safety concern of exposing students directly to the butterfly excrement.

SAMPLE

NOTE Inquiry Master 6.1A differs from Inquiry Master 6.1B: Cabbage White Butterfly—Inquiry, Care, and Maintenance Calendar because it includes tasks that the teacher must perform. Reading Selections For this inquiry, an introductory reading selection, “What Do Cabbage White Butterfly Larvae Like to Eat?” provides students with sufficient information to investigate larva food preferences. “Picky Eaters,” which follows the inquiry, explains the types of cues insects use to choose their diets.

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Reading Selections An introductory reading selection, “Is Color a Factor in Attracting Cabbage Whites to a Food Source?” sets the stage for conducting the inquiry. Two other selections, “The Delicate Balance of Life” and “Gypsy Moths: From Invited Guests to Major Pests,” provide additional information about how narrow food choices limit habitats and how ravenous appetites of insect pests can affect our environment.

The Cabbage White Butterfly The life cycle of the cabbage white butterfly is typical of that of most butterflies and includes the stages shown in Figure 6.1.

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1 mm

Female laying eggs

Egg

1 cm

L1—1st instar 1 mm

Adults mating

L2—2nd instar

Adult

SAMPLE

L3—3rd instar

1 cm

L4—4th instar

Adult emerging from chrysalis

L5—5th instar 1 cm Chrysalis Larva forming chrysalis Figure 6.1

Life cycle of Pieris rapae

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Larval Stages The five larval stages, or instars, of Pieris rapae are designated L1 through L5 (see Figure 6.1). Each stage is defined by a new molt, or shedding of skin. You can determine the larval stage by measuring the head capsule width in millimeters and comparing this measurement with the average figures that follow in Table 6.1. Larvae in the first three instars (from the hatching of the egg through the second molt) are very small and delicate and should be handled with extreme care.

L2–L5 (Second Through Fifth Instars) A larva molts two to three times during the first week after hatching. When molting, it seeks a dry site, weaves a fine carpet of silk, attaches to it, and lies quietly. The exoskeleton cracks and the larva crawls out of it (see Figure 6.2). It quickly pumps up its new exoskeleton, which then hardens.

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LESSON 6

Table 6.1 Larval Stage

Average Head Width (mm)

L1 (First instar)

0.32

L2 (Second instar)

0.58

Figure 6.2

L4 (Fourth instar) L5 (Fifth instar)

exoskeleton.

SAMPLE 0.88 1.36 1.98

L1 (First Instar) During the first instar, the larva chews its way out of the egg through a hole in the middle of the top of the egg. It often consumes its shell, then feeds on adjacent eggs on the egg strip, consuming part or all of the eggs and unhatched larvae. The newly hatched larva’s head is relatively large compared with its body length. As the larva grows in length, its head grows more slowly.

NOTE Students measure and record the body length of a cabbage white larva over a period of 3 weeks. With this information and that in Table 6.1, they will be able to do Extension 10, which instructs them to determine the ratio of head width to body length over time.

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By the fourth and fifth instar stages, the larvae are voracious feeders and will consume increasing amounts of tissue of Brassica (members of Brassicaceae or Cruciferae, the cabbage or mustard family of plants) as they grow (see Figure 6.3). COURTESY OF WISCONSIN FAST PLANTS

L3 (Third instar)

This larva has just crawled out of its

Figure 6.3

This leaf shows both eggs and newly hatched

larvae, which have only begun their eating frenzy.

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Metamorphosis The process of transition from egg to larva to pupa (or chrysalis) to adult is known as metamorphosis. During the pupal stage, the pupa appears to be quiescent or sleeping, but profound changes in its form are taking place as the pupa remains attached to its silken carpet. During early pupal development, the soft, green exoskeleton of the pupa hardens and develops brown- and yellow-tinted external ridges. Not all pupae, however, have the same color exoskeleton. The external coloration may depend on the amount of light to which the pupa is exposed and on the color of the surface on which pupation is occurring. Some pupae that form on a dark surface, for example, have a dark, gray-brown, mottled exterior.

SAMPLE

Note the fine silk threads the larva produced

to attach itself to a surface.

When gently poked with a toothpick, larvae in the first two instar stages detach from the substrate and suspend themselves by a silk thread. Larvae in instars 1–3 may be transferred by picking them up while they are suspended by their silk threads. This can be done with a cotton swab or a small, fine-hair paint brush. Do not grip them with your fingers at this stage; you may accidentally crush them. Defecation Larval excrement is called frass (see Figure 6.5). Under a microscope, frass looks watery. It dries to fine, black granules. A fresh piece of frass is generally the same color as the leaves that the caterpillar has eaten. Examination of the frass through a microscope reveals that the cell walls of the Brassica tissue remain intact, indicating that the larva uses only the nutrients within the cells.

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Figure 6.4

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TO

The frass can be dried and used as fertilizer for the Fast Plants. This is an excellent way of showing how substances are recycled in nature. If the frass accumulates and is allowed to sit in a moist, warm location, fungi will develop and begin to decompose it. Viewing the aged frass under the microscope allows students to see these fungi.

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Silk Production Larvae have silk glands in their heads. Larvae often produce a silk pad on the surfaces, such as leaves or plastic, to which they cling with their legs. They display a characteristic head movement, swaying back and forth to create continuously overlapping “figure eights” from the silk glands. These silk pads are easily seen on the wall and ceiling surfaces on which they are formed, as shown in Figure 6.4.

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Figure 6.5

As the larvae feed on this cabbage, the

frass accumulates at the bottom of the cup. Within days, fungi will begin to form on the frass.

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Hardening of the exoskeleton takes several hours. Because the exoskeleton of the pupa is relatively transparent, the development of various external and internal features can be viewed easily. About 2–3 days after the larva has reached the green pupal stage (the actual time depends on the temperature), the outlines of its wings begin to appear as faint yellow or cream-colored areas on the two sides of its anterior end. The cream color intensifies over the next 2 days as the pupa develops to the yellow pupal stage. One or two dark wing spots appear in the center of the wings and a dark spot appears at the tip of the wing. The pupae in Figures 6.6 and 6.7 are pictured in order of their degree of development. Having reached this pupal wing spot stage, the butterfly is within 24 hours of emerging. As emergence approaches, the pupa takes in air and accumulates fluids in its rear (posterior) region. The pupa appears somewhat swollen. Eyes become evident, and body hair becomes apparent under the anterior ridge between the two eyes.

Adults emerge quite rapidly, sometimes in less than a minute. The exoskeleton splits above the head and the front legs emerge, pulling the body out and away from the pupal case. The newly emerged adult then walks to the highest location, hangs quietly, and allows its wings to expand and harden. Wings usually take about 15 minutes to expand and another 1–2 hours to harden. Adult Anatomy The cabbage white butterfly, being an insect, has a three-part body, consisting of the head, thorax, and abdomen. Within the head region are the compound eyes, antennae, and mouth parts. Even though the cabbage white has a pair of large, compound eyes, it is believed that these butterflies can perceive a single image fairly clearly. Not only can they see the visible spectrum of light as humans can, they also can perceive the ultraviolet wavelengths of the color spectrum. The cabbage white has a pair of antennae covered with small pits that are actually organs of smell. These organs enable the butterfly to locate food sources by their scent. The mouth, or proboscis, of a cabbage white functions solely to take in water and nutrients. The proboscis, located below and between its eyes, is an elongated feeding tube that can be

Figure 6.6

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SAMPLE

This is how pupae change as they develop. The one

on the right will soon emerge as an adult butterfly.

NOTE The images in Figure 6.6 and 6.7 appear in color in Lesson 18 of the Student Guide.

Figure 6.7

A lateral view of four pupa from early to late

stages of development.

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most of the organs of the circulatory, respiratory, digestive, and reproductive systems. Six or seven pairs of tiny holes called spiracles on the sides of the abdomen facilitate the exchange of gasses, that is, the passage of oxygen into the body and the removal of carbon dioxide wastes from the body’s tissues. The heart is a muscular tube that runs the length of the abdomen dorsally. Figure 6.8 When the butterfly finishes feeding, the proboscis will This tube pumps blood toward return to a coiled position. the front of the body. Unlike Lumbriculus, the circulatory syscoiled or extended through the use of special tem in insects is open, with all the internal muscles (see Figure 6.8). The length of the proorgans bathed in blood (called hemolymph). boscis varies greatly among butterfly species The female’s abdomen is larger than the male’s and according to the types of flowers that are to accommodate the large number of eggs that the primary food source. develop. The cabbage white’s body parts are The thorax of the cabbage white bears two shown in Figure 6.9. pairs of wings and six legs. The legs protrude from the underside of the thorax. Each of its feet has a pair of claws and two functions. First, they enable the insect to cling to perches. Second, they contain hair-like, sensory structures, which are responsible for its sense of Wing taste. When these structures detect food, the cabbage white will uncoil its proboscis and attempt to feed. The cabbage white’s two forewings and two smaller hind wings, which protrude from the thorax, are very large in proportion to the rest of its body. The wings are covered with scales. This unique feature is responsible for the Antenna name Lepidoptera, the order of insects to which butterflies belong. “Lepid” means scale, and Eye “ptera” means wing. Scales contain the pigProboscis ments that give the butterfly its color. They also serve as insulation for the body, and because Leg they readily detach when handled (the dust you see on your fingers after you hold them), these scales can facilitate a quick escape from spider Head webs or the grasp of predators. Abdomen Thorax The butterfly’s tube-like abdomen consists of about 10 segments. The abdomen contains Figure 6.9

SAMPLE

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Sex Determination The cabbage white is unusual among insects in that it is possible to recognize sex differences in its larval stages. The testes of the males appear during the third through the fifth larval instars as a pair of small, dark, bean-shaped organs visible in the posterior third of the larvae, as seen in Figure 6.10. It can be difficult to distinguish the sex of adult cabbage whites, but it can be done with careful observation and practice. Males usually have one black spot on the inner forewing, while females have two, as shown in Figure 6.11.

Figure 6.10 The translucent quality of the larva’s skin enables you to

see the male’s testes as two, dark bean-shaped structures.

SAMPLE Female

Male

Figure 6.11 The spots that identify male and female adult cabbage whites

become more pronounced as the butterflies get older.

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Mating Behaviors When adult butterflies are ready to mate, the male joins the female or bumps her with his wings or body. This may be because they sense each other’s pheromones while they perform this ritual. Butterflies bring the tips of their abdomens together in a coupling position, as shown in Figure 6.13. The mating can last from a few minutes to several hours. The male holds tightly to the female Figure 6.13 If disturbed while mating, these butterflies can maintain with structures called claspers on this position even during flight. his abdomen. The male passes a package called a spermatophore through his penis to the female. This package contains both sperm and nutriSTUDENT MISCONCEPTIONS ents, which help nourish the female as she lays Students often expect adult insects to grow her eggs. larger. Help them appreciate that there is no After the female receives the package of such thing as a baby butterfly. Adult butterflies sperm and nutrients, she engages in mating do not get larger even if they eat large quantiavoidance behavior. When she alights on a ties of food. flower, leaf, or other surface, she extends her abdomen in an upward direction, signaling that she is no longer available. If she continues to be SPECIAL NOTE FROM CAROLINA BIOLOGICAL pestered by males, she flies upward quickly in a SUPPLY COMPANY spiral pattern. The males flying after her tend Because cabbage white caterpillars are pests on to wear out first and cease their pursuit. The a number of crops, their use is regulated by the female then returns to search for a good leaf on United States Department of Agriculture which to lay her eggs. (USDA) and by various state agricultural departments. The USDA reserves the right to Feeding Behaviors inspect the conditions under which the insects The sugar, water, minerals, and other nutrients are kept. found in floral nectar are the primary source of The USDA requires that anyone raising cabsustenance for adult butterflies during their quest bage whites follow several safeguards to avoid for mates and for suitable plants on which to lay their accidental release: their eggs. Water and energy from sugar are essential for survival; without them, the butter• To ensure that no eggs or larvae grow in disflies die in a few days. Many exciting questions carded wrappings, you must destroy the and investigations may arise from observing the packaging materials in which your shipment feeding of cabbage white butterflies. arrived.

SAMPLE

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• The eggs, larvae, and live butterflies must stay in your laboratory. • The caterpillars and adults must be kept in escape-proof containers and the room in which you keep the cultures should have window screens to prevent escape to the outside. • Students MAY NOT take the insects home.

Inquiry 6.1 Observing and Measuring a Cabbage White Butterfly Egg and Larva

Humane Disposal When you have completed this unit, DO NOT release the butterflies into the environment. It is not environmentally responsible to release cultured organisms into nature as they may carry genes that could affect the wild population. Since the adult life span of the butterfly is short, you may wait until they die naturally to dispose of them. Otherwise, eggs, larvae, and adult butterflies can be humanely euthanized by placing them in a freezer for 48 hours. Consider saving the dead adult cabbage whites in a plastic cup with holes punched in the lid. They are ideal specimens to examine through the microscope.

For the teacher 1 copy of Inquiry Master 6.1A: Cabbage White Butterfly—Inquiry, Care, Preparation, and Maintenance Calendar 1 sheet of transparent rulers 1 Color Transparency 6.0: Life Cycle of the Cabbage White Butterfly 1 piece of newsprint or 1 transparency* 1 black permanent marker 2 butterfly houses 8 cabbage white butterfly egg strips 8 growing systems with radish plants

MATERIALS FOR INQUIRY 6.1

SAMPLE

NOTE Because the three inquiries in this lesson are conducted over a 1-month period, the “Getting Started” components are imbedded within each inquiry. Appendices D and F give instructions concerning early preparation of equipment and materials for Lesson 6. Check the appendices again to confirm that you have completed all early preparation for Lesson 6 before you start these inquiries.

For each student 1 copy of Student Sheet 6.1A: Template for Drawings of Cabbage White Egg and Larva* 1 copy of Student Sheet 6.1B: Tracking the Growth of a Cabbage White Larva* 1 copy of Inquiry Master 6.1B: Cabbage White Butterfly—Inquiry, Care, and Maintenance Calendar* For each group of 4 students 1 organism photo cards 2 cabbage white butterfly egg strips 2 compound light microscopes* 2 plastic slides 2 transparent rulers 2 hand lenses 2 petri dishes 1 black marker 2 dissecting needles 2 metric rulers, 30 cm (12″)

*Needed, but not supplied

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PREPARATION FOR INQUIRY 6.1 1. Make one copy of Student Sheet 6.1B: Tracking the Growth of a Cabbage White Larva and of Inquiry Master 6.1B: Cabbage White Butterfly—Inquiry, Care, and Maintenance Calendar for each student. Make two extra copies of the latter and either laminate them or protect them between clear plastic sheets. Tape one to each butterfly house. 2. You will need two waxed paper strips with 15–20 butterfly eggs for each group in your first class. As long as students are careful with the strips, they may be used by all of your classes. Your strips will be shipped to you in 4-cm or longer pieces with at least 40 eggs each. Therefore, you will need to cut them in half, making sure eggs and newly hatched larvae are on each one. Make a few extra strips in case some get damaged. Keep the strips in a warm, dry container until they are to be used. 3. Title a transparency or piece of newsprint “Butterflies,” and put it in a convenient place for “Getting Started.” 4. Place your butterfly houses with the eight radish growing systems in a convenient location for students. 5. Just before your first class, put a waxed paper strip of eggs in the base and in the lid of a petri dish for each group and put them in a convenient place for students. The strips of eggs and larvae should be placed on a leaf of the radish growing systems of each group when all classes have completed the inquiry.

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Getting Started students work in groups to list in 1. Have their science notebooks three things that they already know about butterflies. students take turns reading aloud 2. Have “Introducing the Cabbage White Butterfly,” which appears at the beginning of Inquiry 6.1 in the Student Guide. When they have completed the reading, ask them to add to their lists any new information they have learned. time for students to share their 3. Allow lists with the class. Record their responses on newsprint or a transparency. Encourage students to add to their lists any new information shared by their classmates.

SAMPLE

NOTE You must wait until some eggs begin to hatch before conducting this inquiry. Students then will be able to see and draw both the eggs and the newly hatched larvae from the same waxed paper strip. Use a hand lens, if necessary, to observe that some eggs have hatched.

PROCEDURE

your transparencies to go over 1. Use Procedure Steps 1–10 with students. Encourage them to be very careful with the strips of butterfly eggs. Ask students to follow carefully the procedures for using their transparent rulers. Suggest that they adjust the placement of the rulers while observing them through the eyepiece in order to get the most accurate measurement. students that they will be measuring 2. Tell the body length of a larva every 3 days for approximately 3 weeks. Each student who takes this measurement will record it on Student Sheet 6.1B and will share the data with the rest of the group. Explain that students will use these data to determine which time period has the greatest growth rate of the cabbage white.

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Since the larvae are all recently hatched, it should not make much difference which larva is measured every 3 days. They should be sufficiently similar. Have students graph their results on the second page of Student Sheet 6.1B. NOTE If the larvae begin to form their chrysalises before 3 weeks have passed, have students cease their measurements. identification purposes, assign each 3. For Fast Plants light house a number. If you have more than one class, have your last period use a marker to print that number on their radish growing systems before they place them in a butterfly house. Remind them that they and other groups sharing a plant light house will be responsible for maintaining their radish growing system in the butterfly house as well as their Fast Plants growing system in their light house.

REFLECTIONS Have students answer the following questions on Student Sheet 6.1A and then discuss them as a class: A. List the three main body parts of an adult butterfly. If necessary, refer to the reading selection “Introducing the Cabbage White Butterfly” at the beginning of this lesson. (The three body parts are the head, thorax, and abdomen.) B. Did you see all three insect body parts in the larva? Explain. (The larva’s body only has two parts—the head and the body.) C. According to the maintenance calendar on Inquiry Master 6.1B: Cabbage White Butterfly—Inquiry, Care, and Maintenance Calendar, approximately how many days is it from the time the egg hatches until an adult butterfly emerges from its chrysalis? (According to the calendar, the process will take 22–26 days. Take time to review and discuss the calendar with students.) Display Color Transparency 6.0: The Life Cycle of the Cabbage White Butterfly. Show students the correlation between the calendar and the cabbage white’s life cycle.

SAMPLE

to students that they must keep 4. Explain their radish plants in different houses

than the Fast Plants so that the larvae do not eat the Fast Plants leaves. students in each class except your 5. Tell last to turn off their microscope lights, but leave the petri dishes and waxed paper strips on the microscope stages when they have completed the inquiry. Have students in the last class lay the waxed paper strips on a leaf of their radish growing systems and return the systems to the butterfly houses. students update the organism photo 6. Have card for the cabbage white butterfly.

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Inquiry 6.2 Food Preferences of a Cabbage White Butterfly Larva MATERIALS FOR INQUIRY 6.2

For the teacher 1 piece of transparency or newsprint* 3 shallow containers for holding spinach, lettuce, and Fast Plants leaves* Figure 6.13 Slowly and gently lift the larva from the

For each student 1 copy of Student Sheet 6.2: Larva Food Preferences* For each group of 4 students 1 organism photo cards 1 cabbage white butterfly larva 1 Fast Plants leaf* 1 lettuce leaf* 1 spinach leaf* 1 petri dish lid or base 1 piece of filter paper 2 cotton swabs 2 compound light microscopes* 2 plastic slides 2 coverslips 2 dissecting needles 2 plastic pipettes 1 pair of scissors Tap water*

radish plant.

the larva. Then, slowly and gently turn the swab counterclockwise to burrow under the larva and lift it without hurting it, as shown in Figure 6.13. Reverse the procedure to set it back down. 3. Each group of four students will need at least one Fast Plants leaf, one piece of lettuce, and one piece of spinach, all about the same size. Since the larvae will probably eat the Fast Plants leaf, you will need extras. Set up three containers with a thin layer of water on the bottom. In the first container, put at least 10 Fast Plants leaves for each class. In the second, put eight lettuce pieces, and in the third, put eight spinach pieces. If the lettuce and spinach pieces do not dry out, you may reuse them with other classes. Keep extra spinach and lettuce on hand. Be prepared to address students’ requests for additional equipment. 4. Place the containers with the Fast Plants, lettuce, and spinach leaves in a location convenient for students.

SAMPLE

PREPARATION FOR INQUIRY 6.2 1. Explain to students that they will work in groups to design and conduct their inquiry but in pairs to observe the frass. 2. Practice using the cotton swab to pick up a larva so you can demonstrate this skill to students. Hold one end of the swab while you place the other end lengthwise against

NOTE If you are following the recommended sequence of lessons, you will teach Lesson 10 after Inquiry 6.2. The preparation for Lesson 10, however, is at the end of Lesson 9.

*Needed, but not supplied

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Getting Started

method may be more reliable, but do not inform the students of this at this time.)

students complete Step 1 of 1. Have “Getting Started.”

how to pick up and trans4. Demonstrate port the larva from the radish plant to the

with students the reasons these 2. Discuss particular foods are appealing to them. Possible reasons include taste, aroma, and appearance. from students what they think 3. Elicit would attract insects to certain types of foods.

petri dish and back. students how to pick up a piece of 5. Show frass with the tip of a dissecting needle. The frass should readily stick to the needle upon contact.

6. Explain your procedures for cleanup. students update their organism 7. Have photo cards for the cabbage white.

PROCEDURE a student volunteer read aloud 1. Have “What Do Cabbage White Butterfly Larvae Like To Eat?” at the beginning of this inquiry in the Student Guide. Answer any questions students have.

SAMPLE

the transparencies to go over 2. Use Procedure Steps 1–11 with students.

students work in groups to design 3. Have their inquiries. Allow groups time to share their ideas with the class. Possible methods of inquiry they may consider include: • Spacing the three types of leaves evenly around the inside edge of the petri dish, then placing the larva in the middle of the dish and observing which leaf it moves to and eats. • Spacing the three types of leaves evenly around the inside edge of the petri dish, then placing the larva on each leaf for a specified period of time to see which one it will eat. (If the larva is hungry, it will eat only the Fast Plants leaf. Since the larvae are attracted by odor and taste, this

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SAFETY TIP

Instruct students to wash their hands thoroughly with soap and water after handling the frass of the butterfly larva.

REFLECTIONS Have students answer the following questions on Student Sheet 6.2 and then discuss them as a class: A. Which species of leaf did the larva eat? How did this choice relate to where the butterfly lays its eggs? (Assuming the larva eats at all, it will eat the Fast Plants leaf and not the lettuce and spinach because the latter two are not in the cabbage family.) B. What did you observe in the frass of the butterfly larva? Explain. (Larvae absorb the liquid contents from the cells of the leaves they consume, but the cell walls remain intact. Therefore, the frass

LESSON 6

looks like a mass of green cells under the microscope.) C. Refer to the reading selection “Picky Eaters” and list at least two factors that influence how insects choose their diets. (The two factors addressed in the reading selection were odor and taste.)

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PROCEDURE a volunteer read aloud “Is Color a 1. Have Factor in Attracting Cabbage Whites to a Food Source?” in the Student Guide. Then go over Procedure Steps 1–8 in the Student Guide. students’ attention to the white 2. Direct copy paper that you put on the bottom

Inquiry 6.3 Exploring Food Color Preferences of the Cabbage White Butterfly MATERIALS FOR INQUIRY 6.3

For each student 1 copy of Student Sheet 6.3: Food Color Preference Data Sheet*

of the butterfly house. Explain that the photocopies in the plastic boxes were made from a similar piece of paper from the bottom of a butterfly house that had four feeders—one for each color. a group discussion, elicit from stu3. In dents what the drops are and why there are different colors. On the basis of what they learned from “Is Color a Factor in Attracting Cabbage Whites to a Food Source?” students probably will conclude that the colored drops represent excrement from the different colors of sugar-honey-water. If they do not, explain this to them. Ask students how they can determine the butterflies’ food color preferences. Students probably will conclude that counting the number of drops of each color would be the best way to determine food color preferences. If they do not reach this conclusion after a few minutes of class discussion, point out this fact to them.

SAMPLE

For each group of 4 students 1 organism photo cards 1 photocopy of butterfly droppings 1 metric ruler, 30 cm (12″) 1 black marker

PREPARATION FOR INQUIRY 6.3 To protect the sheets of colored butterfly dropping, consider either laminating them or placing them in clear plastic sheet protectors.

Getting Started students work with their groups to 1. Have complete Step 1 of “Getting Started” in the Student Guide. a classroom discussion of stu2. Facilitate dents’ responses.

students to work with their groups 4. Ask to count the number of different color drops. Let students decide how to divide the duty of counting the different color drops. Explain that students should treat the photocopies carefully because they may be used by other classes.

*Needed, but not supplied

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students finish counting the drops, 5. When have a student from each group read aloud the group’s data for each color. Have students copy these numbers onto Student Sheet 6.3 and then calculate the average number of each color of drops. Tell them to refer to these data when they answer the questions in “Reflecting on What You’ve Done.” the class finishes early, have students 6. Ifread “The Delicate Balance of Life” at the end of this inquiry. This is part of their homework assignment for this period.

REFLECTIONS Have students answer the following questions on Student Sheet 6.3 and then discuss them as a class:

may ask about the discolored drops sprinkled throughout. Ask students where they think they came from. In fact, some of the butterflies may have fed on the nectar from the flowers of Fast Plants that were placed in the box and this may have affected the excrement color. Also, the butterflies could have fed on more than one nectar source over a short period.) C. What factors involved in the setup of the feeders and butterfly house do you think needed to be controlled in the preparation of the paper with the different colors of drops? (Answers will vary. Students may suggest that there be no barriers to intercept the drops as they fall. They may see that a combination of the colors of drops are concentrated in certain areas. Since butterflies seem to fly around the area of the light much of the time, there may be many more drops just below that area. To control this variable, the box would need lights uniformly distributed at the top of the box. Also, the feeders need to sit along opposite edges of the paper. More drops would accumulate in these places because the butterflies excrete as they feed.)

SAMPLE

A. According to your data, did the butterflies prefer one color of nectar over another? If so, which color? (Go over the total number of drops of each color that students counted. Normally, the butterflies show no color preferences. If one color shows up in significantly greater numbers, the manner in which the droppings were collected may be suspect. If the total for each color varies greatly from group to group, the counting techniques need to be examined, as each sheet is identical.) B. Did the photocopy of the butterfly droppings have any color of drops other than the original four colors? Explain why you think this happened. (Students

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D. Refer to the reading selection “The Delicate Balance of Life” at the end of this lesson to learn about other organisms that depend on a specific type of food for survival. Explain how an organism’s limited diet narrows its number of habitat choices. (Have students discuss the way in which food choices influence an animal’s habitat.)

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HOMEWORK

Period 1 Remind students that they will be working with Lesson 7 at the end of this inquiry. Have them read the Introduction to Lesson 7.

2.

Have students design and conduct an inquiry to find out if cabbage white larva will eat other plants if no plants from the mustard and cabbage family are available.

3.

Have students determine by observation how to tell a male adult cabbage white from a female. Ask them to report their findings to the class.

4.

Have students prepare two similar Wisconsin Fast Plants growing systems. Instruct them to pollinate the flowers in one system by hand (as explained in Lesson 9). Then have them place the second growing system in a butterfly house for adult butterflies to pollinate. Ask them to compare the number of seeds they harvest from each growing system, put their data into table form, and present their findings to the class.

■ Science

Period 2 Have students read “Picky Eaters” at the end of Inquiry 6.2 in the Student Guide. Period 3 Have students read “The Delicate Balance of Life” and “Gypsy Moths: From Invited Guests to Major Pests” at the end of Inquiry 6.3 in the Student Guide.

■ Science

EXTENSIONS

SAMPLE

■ Science

students to conduct research about 1. Ask the similarities and differences between

moths and butterflies. Ask them to make a table or chart to show their findings. (The chart that students make may look something like Table 6.2.)

Table 6.2 General Differences Between Butterflies and Moths Characteristics

Butterflies

Moths

Antennae

Club-like with a swollen tip

Feathery

Color

Usually bright

Usually duller than butterflies

Resting stance

Wings erect and held together

Wings open and folded over back, looking like the train of a wedding gown

Period of activity

Usually active during the day

Usually more active at night

Pupa

Pupate as an unprotected chrysalis hanging from a branch or other support

Protected by a cocoon or pupate underground or on the ground

Body

Slender

Stouter or heavier

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■ Science ■ Technology

5.

E. Observe other body parts through the microscope.

Ask students to browse the Internet for sites devoted to butterflies. Have them prepare a list of sites to share with their classmates. The name and address of each site should be listed and each should be accompanied by a brief explanation of what can be found there.

Have students record their findings in the form of notes and sketches and make a report to the class. ■ Language Arts

students to write a poem about a 9. Ask cabbage white butterfly or larva. Have

■ Science

them use a form or style that has been addressed in their English class, for example, haiku, limerick, or sonnet.

students design an inquiry to deter6. Have mine whether the concentration of sugar in the sugar-honey-water mixture influences feeding. Ask them to conduct their inquiries and submit their findings in the form of a lab report. ■ Science

students to design and conduct an 7. Tell inquiry to discover whether feeding is

10.

SAMPLE

influenced by adding strongly scented flavorings to the artificial nectar. Have them submit their findings in the form of a lab report. ■ Science

■ Science ■ Mathematics

Ask students to look at the figures they recorded for the body length of a newly hatched larva and that of a larva just before it forms a chrysalis. Inform them that a newly hatched larva of a cabbage white has an average head width of 0.32 mm, and that just before the larva forms a chrysalis, its average head width is 1.98 mm. Using their own figures and the average figures you have given them, have students determine the ratio of the head width to body length of a newly hatched larva and of a larva just prior to forming a chrysalis. Have them conduct research to find out if the same pattern occurs in humans from infancy to adulthood. Ask them to type or handwrite their findings and submit them to you.

students conduct the following 8. Have inquiry: A. Place a moist paper towel in a container, place a dead butterfly on the towel, then cover the butterfly with a second moist paper towel. B. Put a lid on the container and let it sit for 1–2 days. (If it sits any longer, mold will begin to grow.) C. Estimate and record the length of the butterfly’s proboscis. D. Remove the butterfly. Uncoil its proboscis and measure its length. Compare its actual length with your estimated length.

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called Dyar’s Constant states 11. Athatprinciple for each instar of growth, the head width of the new instar divided by that of the previous instar is always approximately 1.5 mm. Explain this principle to students. Then ask them to use Table 6.3 to determine if Dyar’s Constant proves true with the cabbage white. Remind them to keep in mind that these figures

LESSON 6

are averages. Have them show their work and report their findings to the class.

Table 6.3 Average Head Widths of Instars of the Cabbage White Butterfly Larval Stage

Average Head Width (mm)

Ll (First instar)

0.32

L2 (Second instar)

0.58

L3 (Third instar)

0.88

L4 (Fourth instar)

1.36

L5 (Fifth instar)

1.98

■ Science ■ Technology

students to design a new but12. Challenge terfly feeder or a device on which the butterfly can lay its eggs. Have them present the device to the class.

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ASSESSMENT Assessment for this lesson should be based on the student’s ability to do the following— • Participate in the inquiries and adhere to the directions. • Demonstrate knowledge of the basic anatomy of an adult cabbage white butterfly. • Explain the meaning of the word Lepidoptera. • Explain the stages of the life cycle of the cabbage white butterfly. • Measure the length of an egg and the length of the body of a newly hatched cabbage white butterfly larva. • Measure and record a cabbage white larva’s body length at regular intervals for 3 weeks and determine when the growth rate was the greatest. • Determine the food preferences of cabbage white butterfly larvae. • Determine whether adult cabbage whites are attracted to one food color over another. • Articulate and discuss the problems that arise when an organism with a wide variety of food choices is introduced into a new environment. • Offer responses consistent with his or her knowledge of his or her ability level.

SAMPLE

■ Science ■ Mathematics

students cut green, yellow, and blue 13. Have construction paper into 13-cm × 20-cm pieces, then tape the pieces of paper to the back wall of a butterfly cage. Have them observe whether the larvae show a preference for a particular color surface on which to form their chrysalis. Have students report their findings to the class in the form of a graph that shows how many larvae were on each color of paper. ■ Science

students look up the scientific 14. Have names of lettuce and spinach and the family to which each belongs. Use this information to explain why the cabbage white larvae will not eat the leaves of these plants.

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Inquiry Master 6.1A Cabbage White Butterfly—Inquiry, Care, Preparation, and Maintenance Calendar This calendar lists the approximate number of days after laying the eggs on the leaves of the radish plants that certain events in the life cycle of the cabbage white occur. It indicates approximately when students should make specific observations, how you should prepare for upcoming inquiries, and when students should conduct them. Teachers’ activities appear in italics.

Day 1 Inquiry 6.1, lay egg strips on the leaves of radish plants. Measure and record body length.

2 Eggs hatch.

3 Eggs hatch.

4 Eggs hatch. Measure and record body length.

5

6 Observe condition of radish leaves.

7 First larval molt. Measure and record body length.

8

9 Second larval molt. Observe condition of radish leaves. Purchase Brussels sprouts or head of cabbage.

10 Measure and record body length. Place Brussels sprouts or cabbage leaves on soil of radish growing systems when radish leaves are consumed.

11 Third larval molt.

12

13 Prepare larva feeding chambers if desired (see Appendix F.) Measure and record body length.

14 Purchase spinach and lettuce leaves.

15 Fourth larval molt. Inquiry 6.2: Food Preferences of a Cabbage White Larva

16 Transfer larvae to cabbage or Brussels sprouts. Measure and record body length.

17 Start two Fast Plants growing systems to place in butterfly houses. Observe frass for mold growth.

18

19 Measure and record body length.

20 Beginning of pupal stage.

21

22

23

24

25 Prepare butterfly feeders and place in butterfly houses (see Appendix F). Place two sheets of white copy paper on bottom of the box.

26 Observe emergence of butterflies from chrysalises.

27 Put one Fast Plant in butterfly house. Observe butterfly feeding behavior.

28 Observe butterfly mating behavior. Identify adult males and females.

29 Inquiry 6.3: Exploring Food Color Preferences of the Cabbage White Butterfly

30 Prepare egg depositories for butterfly houses (see Appendix F). Place them in butterfly houses.

31 Observe egglaying behavior.

32 The cycle begins again.

33 Observe a dead cabbage white under the microscope.

34

35

36

SAMPLE

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Name: Class:

Date:

Student Sheet 6.1A Template for Drawings of Cabbage White Egg and Larva

SAMPLE 1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10

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Student Sheet 6.1A (continued) Reflecting on What You’ve Done A. List the three main body parts of an adult butterfly. If necessary, refer to the reading selection “Introducing the Cabbage White Butterfly” at the beginning of this lesson.

B. Did you see all three insect body parts in the larva? Explain.

SAMPLE

C. According to the maintenance calendar on Inquiry Master 6.1B: Cabbage White Butterfly— Inquiry, Care, and Maintenance Calendar, approximately how many days is it from the time the egg hatches until an adult butterfly emerges from its chrysalis?

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Name: Class:

Date:

Student Sheet 6.1B Tracking the Growth of a Cabbage White Larva Directions 1. Write today’s date in the first box under the heading “Date.” In the box below the first, write the date for 3 days later. Continue until you have filled all eight boxes. (For example, if today’s date were December 4, you would put December 4 in the first box, December 7 in the box below, December 10 below that, etc.) 2. Circle the date box below where you think the greatest growth in length will occur. Explain why you picked this date.

Table 1 Body Length Over Time Date

SAMPLE

Larva Body Length (mm)

Features and Behavior of the Cabbage White Larva

(continued)

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Student Sheet 6.1B (continued) 3. Graph your results, including the larva body length and the date the measurement was taken. Then answer the questions that follow.

SAMPLE

(continued)

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Student Sheet 6.1B (continued) Answer the following questions A. During which period of time did you observe the greatest growth in length?

B. Did you see a pattern in the rate of growth? Explain.

SAMPLE

C. How do you think the pattern in the larva’s growth rate relates to the amount of leaf material it consumed?

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Inquiry Master 6.1B Cabbage White Butterfly—Inquiry, Care, and Maintenance Calendar This calendar lists the approximate number of days after laying the eggs on the soil of the radish plants that certain events in the life cycle of the cabbage white occur. Use it as a reminder of (1) when to make specific observations, (2) how to prepare for upcoming inquiries, and (3) when to conduct the inquiries. Day 1 Inquiry 6.1, measure and record body length. Lay butterfly eggs on soil.

2 Eggs hatch.

3 Eggs hatch.

4 Eggs hatch. Measure and record body length.

5

6 Observe condition of radish leaves.

7 First larval molt. Measure and record body length.

8

9 Second larval molt. Observe condition of radish leaves.

10 Measure and record body length.

11 Third larval molt.

12

13 Measure and record body length.

14

15 Fourth larval molt. Inquiry 6.2: Food Preferences of a Cabbage White Larva

16 Transfer larvae to cabbage or Brussels sprouts. Measure and record body length.

17 Observe frass for mold growth.

18

19 Measure and record body length.

20 Beginning of pupal stage.

21

22

23

24

25

26 Observe emergence of butterflies from chrysalises.

27 Observe butterfly feeding behavior.

28 Observe butterfly mating behavior. Identify adult males and females.

29 Inquiry 6.3: Exploring Food Color Preferences of the Cabbage White Butterfly

30

31 Observe egglaying behavior.

32 The cycle begins again.

33 Observe a dead cabbage white under the microscope.

34

35

36

SAMPLE

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Name: Class:

Date:

Student Sheet 6.2 Larva Food Preferences Directions 1. In the space that follows, list the procedure steps you will take to conduct your inquiry. List any materials you will need that are not in the materials list.

SAMPLE

2. Make a chart, data table, or drawing to show the results of your inquiry.

(continued)

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Student Sheet 6.2 (continued) Reflecting on What You’ve Done A. Which species of leaf (or other food) did the larva eat? How does this choice relate to where the butterfly lays its eggs?

B. What did you observe in the frass of the butterfly larva? Explain.

SAMPLE

C. Refer to the reading selection “Picky Eaters” and list at least two factors that influence how insects choose their diets.

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Name: Class:

Date:

Student Sheet 6.3 Color Preference Data Sheet 1. Which color of drop do you predict you will find most often on the photocopy?___________

2. Explain your prediction:

Group

Number of Red Drops

Number of Blue Drops

Number of Yellow Drops

Number of Green Drops

Number of Other Colors of Drops

1

2

3

SAMPLE

4

5

6

7

8

Total

Average

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Student Sheet 6.3 (continued) 3. Prepare a bar graph showing the total number of drops of each color.

SAMPLE

Reflecting On What You’ve Done

A. According to your data, did the butterflies prefer one color of nectar over another? If so, which color?

B. Did the photocopy of the butterfly droppings have any color of drops other than the original four colors? Explain why you think this happened.

(continued)

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Student Sheet 6.3 (continued) C. What factors involved in the setup of the feeders and butterfly houses do you think needed to be controlled in the preparation of the paper with the different colors of drops?

D. Refer to the reading selection “The Delicate Balance of Life” at the end of this lesson to learn about other organisms that depend on a specific type of food for survival. Explain how an organism’s limited diet narrows its habitat choices.

SAMPLE

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