Monarch Butterflies


The Monarch butterfly is known by scientists as Danaus plexippus, which in Greek literally means "sleepy transformation." The name, which evokes the species' ability to hibernate and metamorphize, is actually inspired by the Greek myth of Danaus, in which the daughters of Danaus, king of Libya, flee Libya for Greece in order to avoid marrying their cousins. The long, migratory journey of the Monarch butterflies is reminiscent of the daughters' flight.


Adult Monarchs possess two pair of brilliant orange-reddish wings, featuring black veins and white spots along the edges. Their wingspan is about four inches, and they weigh less than half an ounce. Males, who possess distinguishing black dot (stigmata) along the veins of their wings, are slightly bigger than the females.

Each adult butterfly lives only about four to five weeks. But one of the many wonders of the Monarchs is the annual creation of a unique "Methuselah generation." As autumn approaches in their sites of migratory origin, a very special generation of butterflies is born. Unlike their parents, grandparents, great-grandparents, and great-great-grandparents -- all of whom had ephemeral lives measured only in weeks -- these migratory butterflies survive seven or eight months. In human terms, given our average life span of 75 years, this would be like having children who lived to be 525 years old!

This generation performs the incredible feat of flying from Canada and the United States to the center of Mexico -- after which they begin the northward journey again. Once they reach the United States, a kind of relay race begins: their short-lived offspring, with only four or five weeks to live, continue making the trek northward over several generations.



 General: all groups have the same questions:

1. Compare the terms ecosystem, community, species, and population as they relate to ecology.
2. What is the difference between exponential and logistic growth? What are some density-dependent factors that keep populations from growing exponentially indefinitely? What are some density-independent factors?
3. What is an ecological niche? What happens when two species have identical niches? How does the fundamental niche differ from the realized niche?
4. Explain an example of resource partitioning, and explain how natural selection can lead to character displacement.
5. Describe an example of each of the three types of symbiosis discussed in your text.
6. Explain how energy moves through the living components of an ecosystem (starting with primary productivity and including a discussion of food webs and ecological pyramids).
7. Explain how water, carbon, and nitrogen cycle through ecosystems, and give at least one example for each of how human activities can alter the cycle.
8. Seven different biomes are described in your textbook. If you were in charge of global ecosystem conservation but were told you had to focus all of your resources on preserving two of the seven types of biospheres, which would you choose, and why?


Specific to this Case Study:


  1. Describe the life cycle of butterflies. Why might this life cycle make them particular susceptible to environmental change?
  2. What are the habitat requirements of Monarchs at different points in their life history?
  3. Monarchs are famous for their yearly migrations. Describe this migration. Where do the butterflies go, and why?
  4. What role do Monarchs play in the ecosystem(s) to which they belong? What other values do they have to humans?
  5. How is global warming likely to impact Monarch butterflies?
  6. How is habitat destruction impacting Monarch butterflies?
  7. How has coevolution shaped the biology of Monarchs?
  8. What is mimicry, and how does it relate to Monarchs?