Monarch Butterfly Migration Update: April 25, 2002
Today's Report Includes:
News From the Migration Trail
The migration has now clearly moved into Kansas, Missouri and points eastward at the same latitude. Scattered sightings from as far north as 40N latitude were also reported. Also of importance this week was the apparent sighting of a first spring generation monarch in Brentwood, Tennessee:
Warm Weather Brings on the Milkweed!
What a dramatic change from last week's milkweed map! Many observers noted the unseasonably warm spring temperatures from April 14-20 as the map on the far right shows. It was almost 10F warmer than normal across much of the monarch's breeding range. (These maps are only available for U.S. data.) Significantly, of all the milkweed reported since February, 36% of the sightings occurred during the past 10 days.
New Generation Now on the Wing in Arkansas
Challenge Question asked you to predict when the monarch adult would emerge in Arkansas from the egg laid on March 27th. "I think Jim Edson's #1 monarch of the next generation will emerge on the 1st of May," predicted Collin, a 3rd grader at McKnight Elementary in Pittsburg, PA.
Nice estimate, Collin! Let's check in with Jim. The drum roll please...
On the Lookout for Fresh Wings?
Test Your Talents
As you can see, fresh butterflies should now be appearing across the state of Texas, and in Louisiana, Mississippi and even Arkansas. Please watch for them! Because monarch wings become worn and faded over time, wing condition can be used to approximate age. Harlen and Altus Aschen captured the 3 monarchs pictured below in their backyard. Look carefully at each butterfly, and read and the descriptions the Aschens gave them. (See below.)
Thoughts for Earth Day 2002
In recognition of Earth Day, our "Signs of Spring" report this week reflects on human population growth, and its impact on the natural world. As the graph to the right shows, beginning in about 1750, the Industrial Revolution improved the standard of living so dramatically that the human population began to grow exponentially. In less than 250 years, world population went from under 1 billion to 6 billion people. At current growth rates, we add one million more people to the planet every 5 days. How have humans managed to populate the entire globe? Learn about human invention and population growth from an historical perspective:
What if Monarchs Ruled The World?
Challenge Question #26
As we have seen, a single monarch can produce hundreds and hundreds of offspring. What prevents the monarch population from expanding as dramatically as humans have? Given adequate resources, and no disease or predators, all populations increase exponentially. So what do you suppose happens to monarchs?
Imagine monarchs taking control of the world and changing it to fit their needs. They would not need schools or houses, roads or cars! What do monarchs need to survive? How might they curb death rates and increase birth rates, the way humans have? Write a descriptive paragraph telling what the ideal monarch world would look like. What inventions would be needed to make the whole planet habitable for them? Please send us your descriptions: firstname.lastname@example.org
Reader Concerned: Will Bt Spray for Gypsy Moths Affect Monarchs?
Christine Ballenger wrote last week from Illinois, "Our Forest Preserve District plans to begin spraying several preserves in DuPage Co., Il. for gypsy moths using a bacterial spray that kills larva called Bt. They know it will kill any feeding butterflies or moths but are desperate to preserve the trees. They were told that pheromone flakes will not work unless they are used in conjunction with the Bt spraying. I am very concerned about migrating monarchs and other native butterflies not to mention what might happen to bird and? amphibian populations that eat the dead butterflies and moths. What is your position on this issue?? I would like some information to give to the commissioners. Thanks and please hurry. Spraying begins in two weeks!"
If you were a butterfly expert, how would you answer this question? Before reading Dr. Oberhauser's response below, learn about the gypsy moth life cycle and the pesticide, Bt. Then describe how you think monarchs would be effected.
Here is Dr. Karen Oberhauser's response, "Monarch larvae (or larvae of any other Lepidoptera) exposed to
the Bt spray will be killed, and the number of non-pest lepidpteran larvae that will be exposed to this source
of mortality is probably very high. It is unlikely to affect monarch adults, and also should not affect amphibians
or birds (or any vertebrates) that eat the dead insects.
Discussion of Challenge Question #23
When Do Monarchs Disappear?
We asked, "If you were standing on the ground, do you think you could see a monarch 102 meters high in the sky? How could you test this without leaving the ground?"
Mrs. Nunnally's second grade class in Bedford, NH came up with several creative tests including these:
We aren't quite as adventurous as those New Hampshire students. We pictured making a life-sized butterfly and
testing visibility on the school grounds. One could pace-out various distances and see when the butterfly vanishes.
Try it--and tell us at what distance your butterfly disappeared. (Final Note: When watching migrating monarchs,
you may have noticed that the butterflies' movement helps us to see them. Even when butterflies appear as tiny
specks in the sky, our eye can catch their movement.)
How to Respond to Today's Challenge Questions:
1.Address an e-mail message to: email@example.com