Monarch Migration Update: April 11, 2013
Please Report
Your Sightings!
Report Your Sightings
Monarchs are laying eggs all along the migration trail. How many eggs can one monarch lay—and how does a population grow?

This Week's Update Includes:

Image of the Week
Monarch Butterfly Egg
First Steps
Image: Elizabeth Howard
News: On to Oklahoma!
At last! Strong south winds sent monarchs sailing this week. The leading edge of the migration advanced into Oklahoma, Arkansas, and even Missouri. The northernmost sighting now stands at latitude 37 N.

"First adult monarch flying from plant to plant. Tried to take a picture but it's a very windy day and he was gone quickly!" Angela, Yukon, OK (April 9)

"It was the most beautiful sight I ever saw! After the reports that the population was down it was such a relief to see one." Sarah, Hattiesville, AR (April 8)

Cold Delays Development
Temperatures affect monarchs throughout their annual cycle. Gregg Lee noted this week in northern Texas:

"Cool temperatures are slowing development time, not only of milkweed but also of monarch eggs." One egg took 9 days to hatch as shown in this photo series. Chalk Mountain, Texas (April 6)

Waiting for Next Generation
It takes less than one month for monarchs to develop when temperatures are warm (80°F). However, development time is delayed when it's colder. It has been about one month since monarchs reached southern Texas. Average March temperatures were 60-70°F there, so first generation should begin to appear in Texas soon.

How Many Eggs?
Monarchs have tremendous reproductive potential. The egg chart shows how many eggs one monarch can lay. As you study the migration map, think about the eggs monarchs have laid across the landscape.

Monarch butterfly migration maps
Migration Maps
Monarch butterfly egg
Monarch Egg
Image: Jay Cossey
Monarch Butterfly Development Time: Life Cycle Timing
Development Time
Graphic: Elizabeth Howard
Graph: Monarch butterfly eggs: How many eggs can one monarch butterfly lay?
How many eggs?
Image: Marueen Raquet
Slideshow: How Does a Population Grow?
A female monarch butterfly can lay hundreds of eggs. If every egg survived, the monarch population could grow to a billion butterflies in only four generations.

Essential Question
What limiting factors keep the monarch population from growing exponentially?

The Migration: Maps and Journal
  • Please report your monarch and milkweed sightings.
Monarch butterfly migration map Map of milkweed emergence: Spring 2013 Journal Page

(map | animation | sightings)
(map | animation | sightings)
Next update April 18, 2013