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Monarch Butterfly Migration Update: April 25, 2001

Today's Report Includes:

Highlights From the Migration Trail
The big news this week is how little migration news there has been! Last year at this time, monarchs had spread to a latitude of about 40N, with scattered sightings as far as 42N. This year there have been fewer sightings, and the leading edge of the migration is lagging behind last year's by about 4 degrees latitude--some 260 miles. As the migration map shows, the migration from Mexico has spread to about 36N, with a few scattered sightings as far as 38N.

To view both maps simultaneously, open two windows of your browser (Netscape, Internet Explorer, etc.)

This Year
April 25, 2001

Last Year
April 26, 2000

But thanks to 2nd grade students at Hollywood Elementary, we have the first news of a monarch in Maryland. "This was reported to us today, by a naturalist who works with us," they said.

We also have our first sightings from Kentucky this week, contributed by La Grange Elementary. "One student reported a sighting during recess while at school, and another child reported a sighting after school. Today the students watched a monarch while we were out for recess."

A big thanks to the many people who wrote to say that they are NOT seeing monarchs. It's equally valuable to know that people are actively searching. (Though it's not nearly as rewarding for the observer!)

"We look for monarchs daily," wrote Stiles Point Elementary from Charleston, SC. "The first grade is anxiously awaiting our first monarch sighting. We planted a new butterfly garden last week."

If you're watching for monarchs but are not seeing ANY, please let us know. Report to our database as: "Monarch (OTHER observations)"

Discussion of Challenge Questions #22 and #23
Last week's Challenge Questions were designed to help you think about the direction in which the spring migration from Mexico is moving.

How Far From Mexico to Virginia?
Discussion of Challenge Question #22
Challenge Question #22 asked, "Assuming it flew from the sanctuaries in Mexico (19N, -100W), how many miles did the monarch spotted in Gloucester, Virginia (37.28 N, -76.33 W) fly?"

Answer: 1903 miles (3063 km)
(Gloucester, VA is 1903 miles from the sanctuaries, measuring "as the crow flies." However, because monarchs probably don't cross the Gulf of Mexico, if you measure the over-land distance along the Gulf states, you'd find that the VA monarch actually flew more than 1900 miles.)

What If That Monarch Had Flown Due North?
Discussion of Challenge Question #23
Places like Oklahoma, Kansas, Nebraska and the Dakotas are directly north of the sanctuaries. You may have predicted that the migration would move straight north! The answer to Challenge Question #23 illustrates how much shorter that route would be.

Challenge Question #23 asked, "If, instead of going to Virginia, that same monarch butterfly had flown the same distance DUE NORTH from Mexico where would it be?"

Answer: Bismarck, North Dakota (46.48 N, -100.47 W)
A monarch could fly all the way to Bismarck, North Dakota if it flew 1900 miles due north from the sanctuaries. The distance to Bismarck from the sanctuaries in Mexico to is 1917 miles (3085 km), roughly the same distance as from Mexico to Gloucester, VA.

Why do you think the monarch migration moved to the east through the Gulf states after leaving Mexico, instead of heading due north? (If you need a clue, look at the milkweed map!)
Is Monarch Habitat Ready for the Monarchs?
Latest Milkweed Map

How does the readiness of monarch habitat affect the pace of the migration? How will the availability of milkweed affect the reproduction of the next generation? These are critical questions. Please help find the answer! Keep a close eye on the sky for monarchs--and an eye underfoot for milkweed:

Please report the FIRST MILKWEED to Emerge This Spring!

How Long Have These Monarchs Been Alive?
Challenge Question #24

Think back to when you came to school last fall. You may have raised your own monarchs and sent them on their way to Mexico. If your monarchs are still alive, how old would they be now? The monarchs that over-wintered in Mexico are now in their final days. They've been alive for a long, long time. Let's use this example to see how old they are:

Challenge Question #24:
"Assume a butterfly emerged as an adult last August 25 in New York. For how many days has the butterfly been alive as of April 25, 2001? For how many weeks? And for how many months?"

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

Next Generation Soon on Its Way!
If you live in the north, where monarchs have not yet arrived, YOUR first monarchs of the season will probably be the children of the butterflies from Mexico. The next generation of monarchs is now developing. Depending on temperature, the time for development varies. But an estimated number of days the monarch spends at each stage of development is:
Estimated Development Time

3-5 days


9-14 days


8-13 days

Female old enough to lay eggs

5 days


25-37 days

Look at your migration map for a minute and think about this: There were probably many, many monarchs in each place that one monarch was sighted. And what do you think the FEMALE monarchs were doing at all of those places? (Answer: Laying eggs--LOTS and LOTS of eggs!)

Try This!
Predicting When the First Spring Generation Will Emerge

Learn how to use your migration map to predict when the children of the monarchs from Mexico will emerge. Then see if you can answer Challenge Question #25:

Challenge Question #25:
"When might we expect monarchs to emerge in Arkansas? In North Carolina?"

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

Mass Migration in California--But Are They Monarchs?
All at once, a flurry of reports poured in from California and Arizona describing a spectacular migration.

"For the past 3 days I've noticed monarchs passing through like schools of fish!"

"Monarchs are streaming through Carlsbad and Encinitas today like blowing snowflakes. We first noticed them when we woke up this morning, and they continue to migrate through this coastal town as of 1pm."

"Thousands of monarchs are flying all over the San Diego area today. I saw hundreds of them on my way through Camp Pendleton Marine Base this morning, and am watching many more fly past my office window in Rancho Bernardo. I've never seen them pass through this area before. Amazing!"

Do these sound like typical monarch observations to you, based on what you've experienced so far? Read these observations from California and Arizona and look for clues:

We contacted entomology expert Dr. Adrian Wenner, Professor Emeritus at the University of California, Santa Barbara, CA. "That's easy," he responded promptly. He immediately recognized this as a migration of the Painted Lady butterfly (Vanessa cardui).

Occasionally, population explosions in Mexico will cause massive northward migrations, reports the Northern Prairie Wildlife Research Center. These migrations are sporadic and often enormous, and often follow rainy periods in the deserts of the southwestern U.S. and northern Mexico(Opler and Krizek, 1984).

Try these great links for more information about Painted Ladies:

Try This! Practice With Butterfly Identification

Danaus plexippus
Photo Jim Gilbert

Painted Lady
Vanessa cardui
Photo Peter J. Bryant

Look carefully at these photos of a Monarch and a Painted Lady. It's easy to misidentify butterflies--especially when one is looking for a monarch so willfully. Here's a fun exercise to help you look carefully at butterflies. Pull out your sketch pad and take a close look!

Noticia de la migracion de la mariposa monarca: 24 abril de 2001
As the butterflies fly over your homes, schools and cities, we're sending the news back to the students in Mexico so they can track the migration too. Here is this week's report in Spanish, with an English translation:

Reminder: Symbolic Migration Homecoming is May 11th
The symbolic butterflies are about to begin the last leg of their journey. We've been packing them up, and should have them in the mail to you no later than May 1st. We must mail all packages at once--otherwise, people worry that their butterflies are lost and write to us in concern. Therefore, we plan to have all butterflies mailed by this deadline, so please:

** Mark your calendar:
Homecoming for Symbolic Monarchs: May 11, 2001 **

Journey North
Year End Evaluation
Please share your thoughts

How to Respond to Today's Monarch Challenge Questions:

IMPORTANT: Answer only ONE question in each e-mail message.

1. Address an e-mail message to:
2. In the Subject Line of your message write: Challenge Question #24 (or #25)
3. In the body of the EACH message, answer ONE of the questions above.

The Next Monarch Migration Update Will Be Posted on May 2, 2001

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