Monarch Butterfly Monarch Butterfly
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Monarch Butterfly Migration Update: April 11, 2003

Today's Report Includes:

News From Along the Migration Trail

The migration advanced slowly last week, but single sightings from Missouri, Kansas and Tennessee added those states to the count. Rather than advancing dramatically, butterflies seem to be filling in behind the migration's leading edge.

However, as is typical every April, we receive fewer sightings as the month goes on. Do you know why?

Challenge Question #16
"Why do you think we receive fewer and fewer monarch sightings during the month of April every spring, and then suddenly more in May?"

(To respond to this question, please follow the instructions below.)

The Next Stage of the Monarch Life Cycle
The Larva (Caterpillar)

Did You Know?

  • Larva is the scientific word for caterpillar.
  • Larvae is the plural of larva. (So, "larvae" means "caterpillars")
  • The use of either "caterpillar" or "larva" is correct.
Monarch_Summer2002_049
Can you find the two larvae pictured here?
Across the map where monarchs have been sighted, a new generation is now developing. After 3-5 days as an egg, the monarch caterpillar appears. During the next several updates we'll take a close look at the caterpillar stage.

Monarch larvae spend their lives eating--and growing. In fact, the typical monarch increases in mass by 2,000 times while it's a caterpillar. This amazing change takes place in only about 9-14 days. Imagine gaining 2,000 times your weight as monarch larvae do--and so quickly!

Challenge Question #17
"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.)"

(To respond to this question, please follow the instructions below.)

Video Clip: Caterpillar Feast
The monarch seen eating in this video clip ate 6 leaves the afternoon of his filming. It took only 20 minutes for him to eat the leaf he was standing upon. The next day he changed into a chrysalis. Just look at him eat!

Video Clips and the Scientific Process
Observation is the first step in the scientific process. Scientists themselves sometimes use video to enhance their own, direct observations. With video, they can replay an event, see it in fast or slow motion, make time-lapse observations, document changes, focus more closely, freeze action, etc. Video clips provide an opportunity for students to make authentic scientific observations, too. Here are some suggestions for viewing video clips as a scientist:

Correction: A Case of Mistaken Identity
MXnorthernMar03_Edson009
This is a queen, not a monarch!
After inspecting last week's photo that was labeled as a monarch larva found in northern Mexico, we heard from Mike Quinn, Invertebrate Biologist of Texas Parks and Wildlife of Texas: "This is a queen, not a monarch larva!" he exclaimed.

We apologize for the error, and appreciate the instruction from Mike. How could he tell this tiny larva, only a few millimeters long, was not a monarch? Here's your chance to learn:

What's Wrong With That Picture?
Caterpillar Identification Quiz
Inspect the two larvae below. One is a monarch larva and the other a queen. (These large larvae are at the 5th instar stage, the last stage of growth before the chrysalis forms. However, the same field mark that distinguishes the two can be seen on the tiny larva that was misidentified.)
larva_queen_Quinn Monarch_Summer2002_047
Queen Larva
Monarch Larva

Challenge Question #18
"How can you tell the difference between a monarch larva and a queen? What characteristic can be used to separate the two?"

(To respond to this question, please follow the instructions below.)

Where Did All the Monarchs Go?
Discussion of Challenge Question #14

In the wild, monarchs would never lay this many eggs on a single leaf as they do in captivity. (Photo: Dr. Karen Oberhauser's lab)

Help Monitor Monarch Populations

Volunteers are needed across the monarch's breeding range. Please help!
When looking at monarch eggs last week we asked, "If a single female monarch can lay hundreds and hundreds of eggs, why don't we see hundreds and hundreds of monarch butterflies? What happens to them?"

"Some die before they hatch and some die when they are caterpillars," said Rachel.

Exactly! And scientists--with the help of "citizen scientists"--are only now learning when mortality occurs. Citizen volunteers are studying the backyard milkweed patch as part of the Monarch Larva Monitoring Project (MMLP), coordinated by Dr. Karen Oberhauser and Michelle Prisby. Here are initial impressions from MLMP data:

  • Of all eggs laid, as few as 5-10% survive to the 5th instar stage. (In other words, as many as 90-95% die before reaching the 5th instar.)
  • At the 5th instar stage, mortality such as that caused by the tachinid flies, MLMP data don't catch. However, more and more of the volunteers are collecting late instar larvae to measure parasitism rates. The results are quite variable - samples vary from 50% parasitism in some cases, and in other cases the rates are under 10%.
Exploring Milkweed Ecology
Ecology is the study of interactions between living things and their environment. As you may know, milkweed plays a central role in the lives of monarch butterflies. Here are 8 different animals that also interact with milkweed, in one way or another. This lesson challenges you to match each organism with the behavior described.
Recommended Reading:
New Book By Rea, Oberhauser and Quinn
BookMMM_cover
Milkweed, Monarchs and More
A Field Guide to the Invertebrate Community in the Milkweed Patch

(To Order)
BookMMM_pages

"The milkweed community is a stage for a season-long series of dramas involving a cast of fascinating characters," begins this pocket-sized field guide. The pages that follow are packed with awesome images of the invertebrate world that lives, generally unnoticed, right beneath our noses.

This handy guide introduces the reader to the kinds of creatures that come and go from the lowly milkweed patch, each with a job to do: herbivores, nectivores, scavengers, decomposers, predators, and just plain passers-by. But beyond a simple identification guide, this little book portrays the complex interactions between these backyard creatures and delivers what's promised, "A fascinating glimpse into the complex interdependence of life on our planet."

The monarch's life begins in a world, one suddenly realizes, that is as intricate and elegant as its migration across a continent is bold and magnificent. Get your copy quickly! The show is about to begin...

Predators and Parasites on the Prowl

Female tachinid fly laying her eggs on the skin of a moth larva.
Photo by Robert W. Mitchell

You don't have to go to Africa to see it. You can explore the predator/prey interactions that monarchs face in your own backyard. You'll be amazed at what you see. I certainly was! Right before my eyes, my monarch caterpillar suddenly split open--and out crawled 3 maggots.

Here is the story of the tachinid fly, a creature that spends part of its life cycle inside a monarch larva. Can you draw the life cycle of both monarch and tachinid fly?

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!

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 # 16 (#17 or #18)
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 18, 2003

 

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