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Monarch Migration Update: May 17, 2000

Today's Report Includes:

Today's Migration Map and Data
The predicted population explosion has occurred--another 49 new sightings were reported this week! (Of all this season's migration sightings, 28% were reported in past 2 weeks.)

Monarchs are insects, you know. And if there's one thing insects can do quickly, it's reproduce. Of the hundreds and hundreds of eggs laid by each female monarch, many have now reached adulthood--and have continued the migration northward.

Monarch Migration Map
Spring, 2000

1st Generation Shown with "X"

Mapping the 1st Spring Generation
How far did the monarchs from Mexico go--and where are their offspring now being seen? This map above on the right shows our estimate. Roughly speaking, you can consider sightings BEFORE May 3rd as monarchs from Mexico, and those on or AFTER May 3rd as their offspring.

Students who are interested in a precise answer to this question should conduct further research:
  • Go to the Monarch database on the Journey North website.
  • Read the comments from each observer. Make note of sightings of "FADED/OLD" butterflies and of "FRESH/NEW" monarchs. If the observer did not include this information, contact her by e-mail for these details.

Looking Back at Spring, 1999
What a contrast between this spring's migration map and that of Spring, 1999! Here's a chance for students to do their own analysis:

Spring, 2000

Spring, 1999

1) Carefully observe the migration maps for both seasons. What differences do you notice? Write a careful comparison between the Spring, 2000 migration, and that for Spring, 1999.

2) Summarize the results and then draw conclusions. For example, you might begin:

  • The Spring, 2000 migration appears to be (ahead/behind) that of Spring, 1999
  • The pace seems to be different by about ___ week(s).
  • In Spring, 1999, Journey North concluded that May 10 was the cut-off date for first spring generation sightings. (See bright red dots.) In contrast, May 3rd was the date for Spring, 2000 sightings. This might have affected the migrations because _____.

Scientist Says: How Scientists Communicate Research Results
One of the most important steps in a scientist's work is sharing research results with other scientists. This is how the body of scientific knowledge is built--and how it constantly changes, as new research findings replace the old. As a way to synthesize your learning this spring, write your own scientific paper based on the Journey North research in which you have participated. This lessons guides you through the steps of writing a real scientific paper:

Milkweed's Not Only for Monarchs
Last summer's milkweed, showing fibers on stem.

Marcy Cunkelman, who lives near Clarksburg, PA, saw a female oriole last week who was
"peeling the milkweed for strips of fibers for the nest. This is why I never totally clear the gardens," she said, "since many of the birds like to use the grasses, herbs and ect for nesting material."

Why do orioles use milkweed? Read about the elaborate nests orioles build--or build your own!

Exploring Milkweed Ecology: Which Creatures are Connected to Milkweed?

As you know, milkweed plays a central role in the lives of monarch butterflies. They can't live without it! (And to think that we call it a "weed.") Ecology is the study of the interactions between living things and their environment. Here are 8 different animals that interact with a milkweed plant, in one way or another. Read the behaviors described below, then see if you can name the correct organism:

Animal Behavior
Tachinid flies
Milkweed Tussock Moth
Milkweed Beetle (or Milkweed Bug)
Monarch Butterfly
Oriole (and other birds)

Behavior A:
Like monarchs, this species lays its eggs on milkweed leaves. Unlike monarchs, who usually lay only a single egg per plant, this species lays a cluster of a dozen or more eggs on a single leaf. The larvae are found in late summer feeding on milkweed. Larvae are not found alone, but are feeding in groups or "colonies." This species does not migrate the way monarchs do. Instead, it over-winters in the cocoon stage.

Behavior B:
These insects feed by sucking plant juices. They feed in colonies and excrete a sugary waste produce called honeydew. They have "plump, pear-shaped bodies and two tubes, or cornicles, which project like exhaust pipes from their abdomens," according to the
Virginia Cooperative Extension Service (VCES) website, where you can see a slide show about these insects:

Behavior C:
This creature eats the seeds and tissue of the milkweed plant. Again from VCES, "These insects have few predators because they concentrate in their bodies the bad tasting compounds found in the sap of milkweed plants. The bugs use the bright coloration to advertise their bad taste. They are one of a small group of insects that have the ability to tolerate the toxic compounds in the milkweed plant. They are therefore important in regulating populations of the [milkweed] plant."

Behavior D:
This species is known to use the stringy fibers found on dead milkweed stalks to build its nest. It uses the stalks of the plants from the previous summer that died back during the winter. This is a good reason not to cut back old milkweed plants, even if they look like "dead weeds."

Behavior E:
These animals feed on a variety of materials, including live and dead insects, honeydew from aphids, grease, etc. They sometimes use milkweed plants as a place to "farm" aphids. (Just as a farmer guards cows for their milk, this species guards aphids for their honeydew.)

Behavior F:
This animal is one of the many insects that pollinate milkweed flowers. If you observe a milkweed flower very closely, you can watch this species arrive at the flowers to drink the sweet nectar. At the same time, the animal's legs will be caught on the unique milkweed looks like a pair of "saddle-bags" carried off on the feet of this species. When this insect visits the next milkweed flower, it delivers the pollination sacs that will pollinate it.

Behavior G:
This animal is a parasite of the monarch butterfly. It lays its eggs on the monarch caterpillar. When the maggots hatch, they burrow through the monarch caterpillar's skin and feed on its internal organs. The monarch caterpillar will die just as the larva of this insect emerges.

Behavior H:
This species uses milkweed as its only host plant (meaning it ONLY lays its eggs on milkweed). Typically only one egg is laid on each milkweed plant, so that the larvae won't compete with one another for food. As an adult, this species again uses milkweed, this time to drink its nectar.

Summer Milkweed Patrol
Visit a milkweed plant regularly this summer, and sketch the different animals you see. Watch how the milkweed plant changes as creatures chew on, suck from, and crawl all over their leaves. How many different animals can you find any that:
  • Lay eggs on the milkweed plant? (Use milkweed as a host plant.)
  • Forage on milkweed leaves, eating the plant material?
  • Forage on the insects that forage on the milkweed leaves?
  • Suck juices from milkweed leaves and seeds?
  • Drink nectar from milkweed flowers?
  • Pollinate milkweed flowers (so milkweed can make viable seeds for reproduction)?
  • Eat milkweed seeds?
  • Use the "downy" milkweed seeds for lining their nests?
  • Carry milkweed seeds to other places (thereby planting milkweed)?
  • Use the milkweed plant for cover or shade?

Monarch Tracking Will Continue into June--With Your Help
Even though the Journey North season ends on June 1, weekly migration data will be provided until the monarchs reach the end of the road.


Please help by sending your observations. Each and every sighting is important, so please don't forget to send yours!

Journey North
Year End Evaluation
Please share your thoughts

The Next Monarch Migration Update Will Be Posted on May 24, 2000.

Copyright 2000 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form

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