Journey North Monarch Butterfly Spring 2003

Monarch Butterfly Migration Update: May 16, 2003

Today's Report Includes:

News From the Migration Trail
Stay Tuned: The Monarch Migration Continues!
Please Help: YOUR Monarch Sightings Are Important
Monarch Life Cycle: What is a Generation?
Challenge Question #28
Try This! How Long Are Human Generations?
Monarch Generations: Which Generation Migrates to Mexico in the Fall?
Year-end Evaluation: Please Share Your Thoughts

News From the Migration Trail

Link to This Week's Data

As predicted, monarch numbers increased substantially since last week’s report, with eighteen new sightings this week compared to nine last. The leading edge of the migration has now reached 42 degrees north, with the westernmost report from Ames, IA, and the easternmost from Holland, MA. Two new states can add monarchs to the list of species that inhabit their states, Iowa and Michigan:

Monarch Spring Migration Route Prediction Chart

Departure from normal temperatures
NOAA

Interesting to note: in the continent’s mid-section, milkweed has now emerged as far north as latitudes 47 N and 49 N! Milkweed is lagging behind in the East where temperatures have been several degrees below normal this spring (see April temperature map). This is an unusual pattern; in most years milkweed in the Midwest lags behind that in the East at the same latitude.

Perhaps most significant: the migration is keeping pace with milkweed in the East, but the monarchs are 300-400 miles behind available milkweed in the continent’s mid-section. Here are the maps, side-by-side, for comparison:


Monarch Migration	Milkweed Emerging

Stay Tuned: The Monarch Migration Continues!
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.

Please Help: YOUR Monarch Sightings Are Important
Even after the first monarchs have been reported from your state or province, we want to hear from YOU when you see YOUR first! The number of sightings reported reflects monarch abundance, so your observations will continue to be important.

Monarch Life Cycle: What is a Generation?
During the past weeks, we’ve watched monarchs go from egg to larva to chrysalis to adult. During the breeding season, this cycle repeats itself over and over. Each complete cycle is called a “generation.”

Monarch Life Cycle

Egg	Larva	Chrysalis	Adult

Insects have very short generations. Fruit flies, for example, complete their full life cycle in less than two weeks. (This is why they’re so useful to scientists studying genetic changes through generations.) A Monarch generation takes about one month, depending on temperatures. What about other species? To find out, you need to know the age of an animal when it first reproduces.

Challenge Question #28
"How long are Bald Eagle generations? How about Manatees and Gray Whales? (Hint: the information for each animal can be found in the FAQ section of the Journey North website.)

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

Try This! How Long Are Human Generations?

Four human generations are pictured here. Can you find the child, parent, grandparent and great-grandparent? These familiar names are the words we use to describe the relationships between generations.

How long are human generations? Draw your family tree (children, parents, and grandparents is enough). Record the year each person was born in each generation. Next, go back and calculate the age of each person when their first child was born. Finally, calculate the average age at which each generation produced their first child.

Back at school, compare the length of generations for the families in your class. According to your class averages, how long is a human generation? Are the generations the same length now as they were for your grandparents? Discuss possible reasons for any differences you see.

Monarch Generations
Which Generations Migrates to Mexico in the Fall?
The monarch’s breeding season begins in March and lasts into fall. During this time, individual monarchs begin to breed a few days after they emerge as adults. They live for only 2-6 weeks, so several generations live and die during the breeding season. The final generation of the season migrates to Mexico in the fall.

The fall migratory generation is very unusual. Those monarchs do not breed until the following spring, when they are 8-9 months old. By the time they breed, they have survived two migrations and a long winter in between. Will the monarchs that migrate to Mexico the following fall be:

their children?
their grandchildren?
their great-grandchildren?
their great-great-grandchildren?

....you have the idea! Calculate the answer using the worksheet below.

Monarch Generations: Which Generation Goes to Mexico in the Fall?

Journey North
Year End Evaluation
Please share your thoughts

How to Respond to Today's Challenge Question:

1. Address an e-mail message to: jn-challenge-monarch@learner.org
2. In the Subject Line of your message write: Challenge Question #28
3. In the body of your message, answer the question above.

The Next Monarch Butterfly Migration Update Will Be Posted on May 23, 2003