Monarch Butterfly Migration Update: April 18,
2003
Today's Report Includes:
- News From Along the Migration Trail
- Why Fewer Monarchs in April? Discussion of CQ #16
- New Generation Now on the Wing!
- Observers: Please Watch the Wings
- Larva Locomotion: A Closer Look
- The Next Step: Some Anatomy
- How Do Larvae Walk?
- Challenge Questions #19 and #20
- How Much Would You Weigh? Discussion of CQ #17
- Caterpillar Identification Quiz: Discussion of CQ #18
- Milkweed Emerging Along the Migration Trail
News From Along the Migration Trail
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But fresh-winged butterflies will soon replace their parents, and continue the migration northward. Now's a good time to print the Migration Route Prediction Chart and be ready to fill in more states as we go:
Why Fewer Monarchs in April?
Discussion of Challenge Question #16
Mrs. Nunnally's second grade class at Peter Woodbury School in Bedford, New Hampshire, believe fewer and fewer monarchs are seen in April because, "the monarchs coming back from Mexico are starting to die. Then more are seen in May because they are new monarchs that came from the eggs that were laid by the first monarchs migrating north from Mexico."
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| Egg |
Larva |
Chrysalis | Adult |
Exactly! And first evidence of the next generation has already appeared in Texas...
New Generation Now on the Wing
"We started having our first monarchs (from eggs found in the wild) eclose this weekend," reported Harlen Aschen from the Texas Gulf coast on Monday, April 14. ("Eclose" means to emerge from the chrysalis.)
In addition, Janis Lentz's Classes in Weslaco, Texas, reported to Monarch Watch, "Our first adult monarch of 2003 emerged on the morning of April 8. We found the egg on native milkweed on March 16, and the monarch formed a chrysalis on March 28."
Observers: Please Watch the Wings
When you report your first monarch this spring, please note the condition of the wings. Are they tattered and torn--or fresh and brightly colored? Let’s see if we can document when and where the first spring generation appears.
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| Harlen Aschen | |
Larva Locomotion: A Closer Look
Those of us impatient to see our first monarch of spring should be glad monarchs migrate by flying, not walking! This video clip shows the process in slow motion.
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But before you watch:
- Describe in writing how you think a caterpillar walks, based on your memory (or your imagination).
- Think about how people walk and write a very careful, step-by-step description. (Have a volunteer walk in slow motion so you can visualize all the tiny changes in the muscles and joints.)
- For homework tonight, watch a dog walk. How does it keep track of all four legs? Wouldn't it be confusing? Do its front legs jump ahead and the back legs follow?
The Next Step: Some Anatomy
All insects have six legs. That includes monarch butterflies, even in the caterpillar stage. This picture shows one side of a caterpillar. If you count, you might think you're seeing 8 pairs of legs. But the leg-like structures you see, in the rear, are not actually legs. They are called "prolegs." A proleg is an appendage that looks like a leg, and acts like a leg, but is not a true leg (embryologically speaking).
How are the monarch's prolegs different from its true legs?
| True Legs | Prolegs |
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How Do Larvae Walk?
NOW, watch the video clip and describe how a monarch caterpillar walks:
- Which of the monarch's legs or prolegs does it move first? Were you surprised?
- How are the legs and prolegs used differently?
- Describe the challenge the monarch faces when walking on a leaf. How is the caterpillar’s method of walking helpful for balance?
- How does the caterpillar's body change as it walks?
- Compare and contrast larva locomotion to that of other animals. (Does a caterpillar slither like a snake? Crawl like a turtle? Hop like a bird?) Use similies to enhance your description.
- If the prolegs could talk, what do you think they would say to each other?
- Generate research questions while you watch. (For example: What is
on the ends of the prolegs? Are they sticky? How can a caterpillar hang
upside down on the bottom of a leaf without falling?)
Challenge Question #19
"How does a caterpillar walk? Send us your step-by-step description of larva locomotion."Challenge Question #20
"From the place it was laid as an egg, how far do you suppose a caterpillar wanders in its lifetime?"
(To respond to these questions, please follow the instructions below.)
How Much Would You Weigh?
Discussion of Challenge Question #17
We asked, "How much would you weigh 9-14 days from now if you gained 2,000 times your own weight? (With your answer, name something that weighs the same amount.)"
Mrs. Swentzel's third grade class from Stanhope (Byram) NJ, took an average weight for the class. We added up everyone's weight and then divided by the total students in the class. We came up with a weight of 74 pounds. We then multiplied this weight by 2,000 and came up with 148,000 pounds. "Wow, what a lot of weight. We can't imagine what it would be like to be that heavy." Next, we brainstormed different types of animals that might be alive today that might weigh that much. They came up with great white shark, a whale shark, 4 elephants, 10 dolphins, and a Blue Whale. Well, we thought the blue whale would be the closest. When we checked, a half grown blue whale would best match our weight. "This is pretty amazing!"
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This larva has just molted to the 5th instar. Can you see its shed skin? |
The larva's skin stretches and stretches during growth. Then, when additional stretching is no longer possible, the caterpillar sheds its skin (it "molts"). The different stages of growth, between each molt, are called instars. A monarch larva goes through five instars before becoming a chrysalis.
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Caterpillar Identification Quiz
Discussion of Challenge Question #18
Last week we asked about the tiny larva that was misidentified. "How can you tell the difference between a monarch larva and a queen? What characteristic can be used to separate the two?"
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| Queen
Larva |
Monarch
Larva |
"Queens have a third pair of tentacles," said Mike Quinn of Texas Parks and Wildlife, when he pointed out our error.
Mrs. Swentzel's third grade class from Stanhope, NJ, observed the two different caterpillars carefully. Look at the many differences they noticed!
"The monarch larva has a large black head and the Queen seems to have a small black face rather than a head. The monarch larva has a light green body coloring while the queen has a little darker green body with what appears to be some spots. It also seems to have some small black spikes and the monarch has none."
Milkweed Emerging Along the Migration Trail
Please help monitor the spring emergence of the monarch's food plant across North America. You'll be amazed at the close connections the migration and this all-important plant. Please REPORT when your milkweed grows!
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Please report the FIRST MILKWEED LEAVES to Emerge This Spring! |
How to Respond to Today's Challenge Questions:
IMPORTANT: Answer only ONE question in each e-mail message.
1. Address an e-mail message to: jn-challenge-monarch@learner.org
2. In the Subject Line of your message write: Challenge
Question #19 (or #20)
3. In the body of EACH message, give your answer to ONE of the questions
above.
The Next Monarch Butterfly Migration
Update Will Be Posted on April 25, 2003
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North. All Rights Reserved.
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