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Butterflies in the Stomach

Is Genetically Modified Corn Harming Monarch Butterflies?


Mariela Cruz Calderón
Life Sciences
Quest University
Annie Prud’homme-Genereux
Continuing Studies and Executive Education
Capilano University


Why is the North American population of monarch butterflies declining? In 1999, a study published in the journal Nature suggested that a variety of genetically modified corn was killing these iconic butterflies. While it was later shown that the conditions in this study did not mirror those in the field, the results garnered a lot of media attention and many people today still believe that monarchs are being killed by GMOs. This case familiarizes students with the plight of the monarchs, encourages them to think about how to test the hypothesis that a toxin is responsible for their decline, and takes a critical look at several studies that investigated the role of Bt corn in the life cycle of monarchs. This interrupted case takes 60-90 min to complete, requires little to no science background, and can be used to explore the ecology and wildlife management of monarchs; risk assessment, toxicity, and exposure; experimental design, the scientific method, hypothesis, and critical thinking; or the relationship between science, the media and the public.


  • Propose hypotheses for the decline of monarch butterflies.
  • Evaluate the strength of evidence for the role of Bt corn in the decline of monarch butterflies.
  • Determine the risks that a poison poses for an organism.
  • Analyze and interpret graphical data.
  • Compare and contrast the strengths and weaknesses of laboratory and field studies.
  • Understand the importance of replicating studies and of merging data from several researchers to make conclusions about a hypothesis.


GMO, milkweed, genetically modified organisms, Bt corn, corn, monarch butterflies, pesticides, Bt toxin, media, risk assessment, exposure, toxicity

Topical Areas

Scientific method, Regulatory issues, Science and the media

Educational Level

High school, Undergraduate lower division, Undergraduate upper division



Type / Methods

N/A, Analysis (Issues), Interrupted, Journal Article



Subject Headings

Agriculture  |   Biology (General)  |   Ecology  |   Environmental Science  |   Science Education  |   Science (General)  |   Toxicology  |  

Date Posted


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