Today's News Report Your Sightings How to Use Journey North Search Journey North

Monarch Butterfly Migration Update: April 4, 2002

Today's Report Includes:

Latest Migration Map and Data

Field Notes from the Migration Trail
It's been 22 days since the sudden first wave of monarchs arrived in Texas. Butterflies were traveling across that big state in big numbers last week, delighting observers on the ground, and even some up higher:

"I was working at my office on the 32nd floor of a building in downtown Dallas. Around 6 in the afternoon I saw 5 monarchs fly past my window in a 10 minute period. The weather was cool and sunny."

How High Were the Monarchs Flying?

Challenge Question #17
?How high in the sky were those monarchs traveling in Dallas? (Please give your answer in meters, and tell us what height you estimated for each floor of the office building.)?

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

First sightings were reported last week from Georgia, Tennessee, and Oklahoma. We even received a very early report from southern Kansas, 230 miles north of any other sighting. Will you include this one on your migration map?

April 1 Wichita, KS
"There was just one lone monarch floating across the street as our safety patrol waited for school to let out. The patrollers were wondering how old it is and what might happen to it on its journey." And after we wrote for confirmation: "I am 90% sure. I thought I was 100% sure until I received your message. It was as like a monarch as I have ever seen, but I couldn't study it. It fluttered across the street in heavy traffic. A while back we had a lot of really windy days, south wind.? Maybe this one rode in on it.? If you are not comfortable counting it then it is ok with me. I will keep looking, but we are now having a little cold streak."

Monarchs Moving Ahead of Milkweed?

The clearest pattern noted during the last week was the impression that monarchs are indeed ahead of their milkweed. Many observers have noted milkweed emergence lagging behind the reports of first monarchs in the region. Full comments are available on the web, but here's their flavor:

Humble, TX
"Butterflies desperately looking for milkweed. All my milkweed froze this winter. I had small plants growing inside which I immediately planted and on inspection a day later, they were covered with eggs."

Caldwell, TX
?I found that many plants had several eggs on them, sometimes as many as ten! This is similar to the mass ovipositing I saw 2-3 years ago."

Westhoff, TX
?An informal count on one hundred stems (average of twelve leaves) yielded one hundred eggs, the one larva, only two doubles."

Jackson, MS
Three adults flew slowly over a 5 acre field continuously for about 10 minutes before moving out of sight. None were observed to stop for oviposition and we found no milkweeds had emerged in this field."

If this is true, it raises very interesting questions about the mechanisms behind monarch migration: Do monarchs follow vegetation readiness? Or do they travel according to a constant, celestial cue regardless of the pace of plant development? Are they simply blown by the winds? These temperature maps show how cool spring, 2002 has been--and presumably how slow the vegetation has been to develop this year--in the regions where monarchs are now traveling. One final note: Monarchs are VERY good at finding milkweed, so they may see what people overlook!

Texas Milkweed (Asclepias asperula) April 7, 2001
Courtesy of
Harlen and Altus Aschen

Egg-loading on Milkweed Noted: Female Egg-Laying Strategy?
The appearance of multiple eggs on a single plant is known as "egg loading." Observers should watch for this whenever they check their milkweed plants, and include these observations with their comments. Egg loading is thought to occur when there is not enough milkweed in an area. What do you suppose the female monarch's egg-laying strategy is?

Challenge Question #18
"Why do you think female monarchs typically avoid laying more than one egg on a milkweed plant? List all the benefits you can think of."

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

Expecting Monarchs in Arkansas
When Will the First Spring Generation Be Born?

On March 27th, Jim Edson caught this worn-looking monarch in Monticello, Arkansas. Assuming she's flown from Mexico, she has over 1,100 miles behind her. And she's probably laid many, many eggs on the milkweed she found along the way.

Jim took her into his lab to have her lay a few more eggs, and to watch the life cycle progress. "She has laid about 80 eggs so far, and about 60 have emerged
as caterpillars. She is doing well and is still laying," he said on April 3.

He's offered to share her story with us each week. This information will help us to estimate when the next monarch generation will emerge across the southern tier of states. Remember, thousands and thousands of eggs have been laid there since the monarchs arrived three weeks ago.

Just think: If you live in the north, the first monarch you see this spring will probably be a child of a monarch from Mexico. Who knows, maybe your own first monarch is an egg or caterpillar developing in Arkansas right now! So print this life cycle chart, and then send us your predictions!

Your Predictions Please!
Challenge Questions #19, #20 and #21

Challenge Question #19
"On what date do you think Jim Edson's first monarch of the next generation will emerge in Arkansas?"

Challenge Question #20
"How many eggs do you predict the female from Mexico will lay in captivity?"

Challenge Question #21
"On what date do you think the female from Mexico (of the over-wintering generation) will die?"

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

What About That North Carolina Monarch?
Discussion of Challenge Question #16

We asked, "How do you interpret the sighting from the coast of North Carolina? Do you think this butterfly came from Mexico? Why or why not?"

"When I looked at a map, I saw almost instantly that it wouldn't happen. It is impossible!" claims Jon of Griswold Middle School, Rocky Hill, CT.

People across the continent put their heads together on this one. They came up with 6 reasons why they thought it?s possible and 16 reasons why it's not.

Among the reasons why they thought it's possible that the butterfly came from Mexico:

  • It might have left Mexico early.
  • One might have flown ahead of the rest.
  • The recent storm and high wind may have blown a monarch off course.

And the reasons why they thought it's impossible or improbable that the butterfly came from Mexico:

  • It might have stayed in North Carolina over the winter.
  • Maybe it was from Florida. They left from Florida to go to North Carolina.
  • I'm afraid someone hatched it.
  • It would be a viceroy. Distinction between the monarch and viceroy has been hard, but a little use of common sense may distinguish between them.

Thanks for the great thoughts contributed by:

  • Mrs. Coats 1st Grade Group at Merrick-Moore Elementary School in Durham, NC
  • Kelsey and Jon at Griswold Middle School in Rocky Hill, CT
  • Mrs. Nunnally's second grade class at Peter Woodbury School in Bedford, NH
  • Ms. DiBara's second grade class at Charlotte Dunning School in Framingham, MA
  • Mrs. Flaherty's second grade class at Charlotte Dunning School in Framingham, MA
  • Ms. Macko's second grade class at Charlotte Dunning School in Framingham, MA
  • Darrell Atteberry, and Pat Thomas, Duluth, MN

As is often the case, along came another sighting from North Carolina. This time from Jeff Pippen of Duke University's Biology Department who also coordinates North Carolina's online butterfly network. (Read, "He must know what he's talking about!")

"I got point blank looks at it for a few minutes as it piddled around in a short grassy lawn. It was fairly worn, but still flew well. My feeling is that it managed to overwinter in the area rather than having migrated up from Mexico. But who knows for sure?"

Notice how the Gulf Stream is deflected off the US coast near North Carolina.

Dr. Lincoln Brower shared these thoughts: "In mild winters, which this one was, some monarchs get holed up on the islands off the North Carolina shore. I think they get stranded during fall migration on those islands along the coast. They don't like to cross water, so reach a dead end. The Gulf Stream isn't too far off the North Carolina shore (see map), so it stays pretty warm during the winter. I think the butterflies hang out over the winter and, if they manage to survive, they probably move back inland. So in a year like this it's ambiguous whether the butterfly is coming up from Mexico or if it's one that just managed to survive the winter."

So, as Dr. Bill Calvert says when nature's patterns don't fit our expectations, "This is so delightfully confusing!" Nobody has the answer--not even the scientists! How would YOU design a research project to shed light on this question?

Try This! Journaling Questions
Look at these climate maps and find out what kind of winter they had in North Carolina from December-February:

Extreme Minimum

Departure from Normal Temperatures

  • What was the coldest temperature this winter, according to the NOAA climate map? Did it ever go below freezing?
  • If a monarch could survive on the North Carolina coast this winter, what other places could they have survived?

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:
2. In the Subject Line of your message write: Challenge Question #17 (or #18, #19, #20 or #21).
3. In the body of EACH message, give your answer to ONE of the questions above.

The Next Monarch Migration Update Will Be Posted on April 11, 2002

Copyright 2002 Journey North. All Rights Reserved.
Please send all questions, comments, and suggestions to
our feedback form

Today's News

Report Your Sightings

How to Use Journey North

Search Journey North