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Wednesday, August 21, 2013

Caterpillars in the Classroom

Spotted Tussock Moth

There are many rituals that teachers perform as they prepare to return to the classroom, and this year, one of those rituals is going to be especially challenging: searching the local milkweed patch for Monarch caterpillars.  For decades, teachers have raised Monarchs in the classroom with their students, but with declines of over 90% this year, Monarchs are currently absent from much of Vermont.  So what is a teacher to do?

The good news is that Monarchs are one species out of hundreds of native caterpillars that can easily be raised in the classroom.  Unlike Monarchs, most other caterpillars won’t emerge as moths or butterflies in the fall, but hold on to the cocoons and your caterpillar will eclose (emerge from its cocoon) in the spring, reinvigorating students months after they’ve forgotten about their caterpillar friends.  Many of the same lessons that we learn from the Monarch can apply to other species: life, death, adaptation and transformation.  This short tutorial will give teachers some of the tools they need to raise caterpillars in the classroom this fall.

Finding Caterpillars

Beautiful Wood-nymph caterpillar
Caterpillars spend their lives doing two things: eating and trying not to be eaten.  This can make finding caterpillars challenging.  But fear not!  If you spend time outdoors doing some targeted searching, you are likely to stumble upon a caterpillar sooner than later.  Here are a few methods for finding caterpillars:

  • Examine foliage for signs of caterpillar feeding, including damaged leaves and frass (caterpillar poop).  The fresher the damage to foliage, the more likely a caterpillar is still nearby. 
  • Use a beating sheet.  Place a white bed sheet beneath vegetation, and then shake the vegetation to dislodge any caterpillars.  If all goes well, a caterpillar will fall onto the bed sheet and be easy to spot against the white background. 
  • Look for caterpillars at night. Many species of caterpillars hide by day and become active after dark, when fewer predators are out hunting for them. 
  • Search with your students.  Having a few dozen eyes helping you search will increase your chances of success, and your students will enjoy the hunt! 
Caution: Some caterpillars, especially those with hair and spikes can sting or cause skin irritation

Raising Caterpillars

Our Promethea caterpillar doesn't even have a tank!
We feed it lilac, white ash, and black cherry.
Before bringing a caterpillar back to the classroom to raise, it is essential to know what that caterpillar eats.  Many species will feed on just one or a handful of host plants (such as the Monarch, which feeds only on milkweeds).  If you find the caterpillar on a plant, it is likely that that plant is a host.  You can collect some branches of the host plant along with the caterpillar, so it has something to feed on.  If you find the caterpillar away from plants, you must identify it in order to determine what it eats.  Keeping a steady supply of host plant available to your caterpillars may be the most challenging part of raising them.

Next, you should try to identify your caterpillar.  There are some great resources on the web to help identify mystery insects, such as the Vermont Atlas of Life.  You can also email a picture to NBNC and we’ll do our best to help with identification.  Knowing what kind of caterpillar you have will shed light on its life history, what special adaptations it has, and what moth or butterfly it will become. 

Our Variable Oakleaf caterpillars have
almost doubled in size since we
found them a week ago
Terrariums that hold caterpillars should be kept clean and well-ventilated.  Provide a constant supply of fresh food to the growing caterpillar.  Research your caterpillar, as there may be tips specific to each species that help ensure successful rearing.  For example, some caterpillars burrow underground to create cocoons and will need a substrate of soil in their terrarium.  NBNC can help, so don’t be shy about letting us know what caterpillars you are raising. 

If you have questions about raising caterpillars, please see the resources below or get in touch and we’ll see if we can help!

Involve Your Students

Be sure to involve your students every step of the way.  Caterpillars grow fast and your students will be excited to see their caterpillars change from day-to-day.  Countless lessons on adaptation, evolution, growth, and change can spur from the raising of caterpillars.  Their progress can be documented with students through art or writing.  Their growth can be measured and graphed, as can the quantity of leaves they consume or frass they excrete.  Our migratory species can even offer opportunities to learn about geography or to find pen pals in other states/countries who share our experience with these delicate creatures.

In Conclusion

This tutorial just scratches the surface of what can be done with caterpillars in the classroom.  The resources listed below provide more tips on identifying and raising caterpillars.  Since much of the school year takes place during the winter months, the window for working with insects is narrow.  The start of the school year offers the best opportunity to raise your “class pet” caterpillars and we look forward to hearing about your experiences in the classroom!

Silver-spotted Skipper caterpillar flaunting its
impressive fake orange eyes
Additional Resources

Champagne, C. 2012. Finding Slug Caterpillars. Retrieved from http://bugguide.net/node/view/668155

Jaffe, S. 2013. The Caterpillar Lab. https://www.facebook.com/TheCaterpillarLab

Wagner, D. 2005. Caterpillars of Eastern North America. Princeton, N.J. : Princeton University Press

Wagner, D. 2011. Owlet caterpillars of eastern North America. Princeton, N.J. : Princeton University Press

Wagner, David L., Valerie Giles, Richard C. Reardon, and Michael L. McManus.  1997.  Caterpillars of Eastern Forests.  U.S. Department of Agriculture, Forest Service, Forest Health Technology Enterprise Team, Morgantown, West Virginia.  FHTET-96-34.  113 pp.  Jamestown, ND: Northern Prairie Wildlife Research Center Online.  http://www.npwrc.usgs.gov/resource/insects/cateast/index.htm  (Version 11APR2001).

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