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Monarch Butterfly Migration Update: May 16, 2002

Today's Report Includes:

News From the Migration Trail

This Year

Last Year


  • Link to Data: Link to This Week's Migration Data
  • The monarchs have now clearly moved into Iowa, and have almost reached latitude 42N in that state. Notice that no sightings have yet been reported from Illinois, Indiana, or Ohio and only a few from the East Coast states. There, early monarchs are as far as 40N.
  • Last year the migration had advanced to 45N in the Midwest, approximately 180 miles ahead of this year?s. The monarchs were much more evenly spread across all longitudes.
  • Monarchs were clearly more abundant last spring. While we have 19 sightings in today?s update, this compares to 44 for the same time last year.

Stay Tuned: The Monarch Migration Continues!

?We still haven't seen the first Monarchs and the milkweed isn't up yet here in Minnesota. Does this mean that we won't be able to record when monarchs arrive, etc??

No, even after school's out, migration-tracking will continue. Other Journey North migrations have come to an end, but we'll continue to track the monarchs until they?ve expanded across their entire breeding range. This normally takes until mid-June, but may take more time this year because the population is so low.

Please Help: YOUR Monarch Sightings Are Important
This is an ESPECIALLY important year to be watching for monarchs. Even after monarchs have been reported from your state or province, we want to hear from YOU when you see YOUR first! And, if you don?t see your first monarch until later in the summer, please report it then. The number of sightings reported reflects monarch abundance, so your observations will continue to be important.

Migration Prediction Contest: The Envelope Please...
Here?s a fun way to watch for monarchs! Ms. Smith from Unity Charter School in Morristown, New Jersey explains: "Our class has a contest going. Two weeks ago students predicted the arrival date of the monarchs into our school garden. They used the information from all of the migration updates to track the monarchs and estimate a date of arrival. We sealed the predictions in an envelope, which will be opened on the day we observe our first monarch. The student who comes closest, without going over, gets to chose the flavor of ice cream for our ice cream party! The winner will also get to input our sighting information into the Journey North web site."

Cool, Rainy Weather: Where Do Monarchs Go When it Rains?
Many people mentioned the cool, wet weather during the past week. A second grader at Lincoln School in Dubuque, Iowa, named Mikey wrote:

?We are studying Monarchs right now and I was wondering, where do they go when it rains??

?When it's raining, monarchs do not fly,? says Dr. Oberhauser. ?Butterflies in my experimental cages hold onto the sides of the cages until it stops raining. In the wild, they hold onto trees or bushes. If wet monarchs get knocked off these perches, they sometimes get stuck on the ground. If they're too wet, they can't fly because their wings are too heavy. However, monarchs do not need to stay completely dry. If they do get wet, they simply remain still until the water evaporates off their body. They often bask in the sun to dry their wings.?

When you?re the size of a butterfly, raindrops can be dangerous! The typical raindrop weighs about 1 gram. Monarchs weigh about a half a gram, on average.

Dr. Lincoln Brower believes this butterfly and moth behavior evolved as an adaptation to rain: "It likely that butterflies and moths rest in the positions they do to avoid damage from rain. Monarchs' positions at the overwintering sites are a good example. Notice how they close their wings over their backs and sit vertically, with heads up. Moths, resting on trees, usually press wings flat against the tree. That?s an adaptation to avoid damage from rain, too."

Try This!

  • If you?ve ever done a belly flop, you know how much changing your body?s orientation to water matters. Hold your arms as if you?re diving into water. How is this similar to the way monarchs hold their wings? Why do you think this makes such a big difference in the force you feel?
  • Luckily, we don?t have to worry about raindrops that are twice our weight falling from the sky. How big would such raindrops be? Here are some helpful facts from the Water Weight Conversion website.

Where Did Your Symbolic Butterfly Land?




We've set up this meeting place. Share the stories of the butterflies you received and find out where your own butterflies landed. Here a link to more students' stories like these:

  • "Hello, My name is Andrew from Waupun, Wisconsin. What a surprise! Your butterfly from Cambria, Wisconsin almost went back to where it came from. The only damage is that one antenna is missing."
  • "Sulphur Rock High School has received butterflies from Mexico! The SRHS students have written letters to the students and are returning the butterflies to the original owner."
  • "Our class in McGehee,Arkansas have received a lot of monarchs to care for this summer! We have received butterflies from all across the United States and Canada. Here are the schools where the butterflies we received."

Noticia de la migracion de la mariposa monarca

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:

Journey North
Year End Evaluation
Please share your thoughts

The Next Monarch Migration Update Will Be Posted on May 23, 2002

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