Monarch Butterfly Migration News

Monarch Butterflies

Here They Come!
May 17, 2017 by Elizabeth Howard

The outburst of 1st Generation butterflies is beginning.

This female in Wisconsin is one of the week's northern-most monarchs.
Sighting and photo by Chris Smith in Hudson, Wisconsin on May 14, 2017

Moving into Minnesota
After a 3-week lull, the migration advanced to latitude 45°N this week. Observers in Minnesota were ready and waiting to welcome the monarchs.

"One adult flying around the Driskill's grocery store and by the library at high speed, about single story roof height. Unable to pinpoint male or female. It was bright, definitely not a Gen Zero (from Mexico)," wrote Patti Keiper from Hopkins, MN on May 14th.

Eggs Across the Landscape
Since their arrival in Texas in March, we've watched for two months as the monarchs from Mexico have laid eggs across the landscape. Now, we're beginning to see the explosive growth of the 1st spring generation. Over the summer breeding season, the population will increase with each new generation.

One monarch could produce a billion butterflies in only 4 generations if all of her eggs survived. In this week's slideshow, explore the limiting factors that keep the population from growing exponentially.

From 43°N to 45°N

Laying Eggs in MN
T. Nowak

From Eggs to Butterflies
How Does a Population Grow?

One female can lay several hundreds of eggs. Let's see how quickly the numbers could grow from one monarch generation to the next.

How Many Survive? One female can lay several hundred eggs. Let's see how quickly the numbers could grow from one monarch generation to the next.

A generation is one complete life cycle. A monarch can complete its life cycle in only one month. Let's count monarch generations and see how long it takes to reach a billion butterflies.

What is a Generation? A generation is one complete life cycle. A monarch can complete its life cycle in only one month. Let's count monarch generations and see how long it takes to reach a billion butterflies.

If all of her eggs survived, one monarch butterfly could produce a billion butterflies in only 4 generations. She would have over a billion great-great-grandchildren!

One Billion Butterflies If all of her eggs survived, one monarch butterfly could produce a billion butterflies in only 4 generations. She would have over a billion great-great-grandchildren!

With such a high reproductive potential, why isn't the world swarming with billions and billions of monarchs? What factors might limit the population size?

What Limits Monarch Numbers? With such a high reproductive potential, why isn't the world swarming with billions and billions of monarchs? What factors might limit the population size?

Monarch numbers can rise and fall for countless reasons. Here are some examples of limiting factors: Temperatures can be too hot or too cold; Precipitation can be too high or too low; Enemies can be many or few; Diseases can be deadly or mild. Food sources can be scarce or abundant...

Limiting Factors Monarch numbers can rise and fall for countless reasons. Here are some examples of limiting factors: Temperatures can be too hot or too cold; Precipitation can be too high or too low; Enemies can be many or few; Diseases can be deadly or mild. Food sources can be scarce or abundant...

Scientists are still learning about the balance between the monarch's high reproductive potential and the factors that limit the population's growth. Probably less than 1% of all monarch eggs become butterflies, yet the population typically gets a little larger with each generation.

Finding the Balance Scientists are still learning about the balance between the monarch's high reproductive potential and the factors that limit the population's growth. Probably less than 1% of all monarch eggs become butterflies, yet the population typically gets a little larger with each generation.

Report Your Sightings You can help scientists learn more about monarch populations by contributing your own observations.

Companion Resources

Driving Question

What limiting factors keep the monarch population from growing exponentially?

Evaluation: Share your thoughts!

Please take a few minutes to complete our Annual Evaluation. With your help, we can document Journey North's reach, impact and value. Thank you!

Journey North Annual Evaluation

Spring Migration 2017


Report all monarchs you see — adults, eggs, larvae.

What to Report	Adults report \| map \| list	Eggs report \| map \| list

Larvae report \| map \| list	Milkweed report \| map \| list	Other Observations report \| map \| list

Next May 18, 2017