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The Cankerworm Explosion of Summer 2021

The Cedar Valley experienced a cankerworm population boom throughout the spring and summer of 2021. The cankerworms coated the campgrounds, sidewalks, and trails of eastern Iowa. Naturalists and park rangers described the amount of them by exclaiming, “The grass is moving!” Although Iowa has seen cankerworms before, this population boom was larger than any years preceding.

Black Hawk Park, Cedar Falls, Iowa

Possible Guiding, Compelling and/or Anchoring Questions

  • How do cankerworms interact with their ecosystem? 
  • What do cankerworms need in their ecosystem in order to thrive?
  • What impact could a cankerworm’s ecosystem have on their migration patterns?

Classroom Suggestions

  • Cankerworms are impacted heavily by their ecosystem (migration relying on wind patterns.) They also impact the ecosystem they live in through feeding damage, building silk threads, and their abundance. These factors could be used to explore how changing conditions in ecosystems can result in the introduction (or reduction) of an organism's presence in that ecosystem. 
  • Cankerworms migrate via silk “balloons” blown by the wind. As an abiotic part of an ecosystem, wind can change the ecosystem of a cankerworm altogether. This phenomena could be used to explore this aspect of ecosystems and create discussion around other aspects of ecosystems.
  • Exploring the behavior of cankerworms (which are actually caterpillars) can be used to support students' understanding of the life cycle of a butterfly.

Related Resources

Iowa Core Alignment


Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem

Credit Info

Submitted by Hartman Reserve Nature Center 2021 Summer Interns: Hannah Bertram, Gabby Hartman, Matt Marvin, Marley Millar


Have you used this resource in your classroom? Do you have ideas for improvement? Share your ideas, experiences and feedback about this phenomena.

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