Creating a Dichotomous Key for Families of Idaho Butterflies
computer exercisesuggested grade levels: 9-12, College
view Idaho achievement standards for this lesson

Teachers should explain how to make a dichotomous key and make a simple one together as a class. As a precursor to this butterfly activity, it would be a good idea to have students make a dichotomous key using inanimate objects such as pencils, paperclips, coins, etc. At each stage in the dichotomous key all remaining "species" must be separated into two clearly distinguishable groups. The splitting must continue until all "species" have been separated out. To see a good example of how this is done, refer to the How to identify species using morphology and creating a dichotomous key in the biology exercise site. This kind of activity works better if students work in groups of three or four, but larger groups can be used depending on how many computers are available in the classroom.

1. Students will learn how to use the butterfly section of the Digital Atlas of Idaho.
2. Students will learn how to make a dichotomous key.
3. Students will hone their skills of observation and learn how to recognize defining characteristics that distinguish different families.

Have your students read through the section on "How to identify species using morphology and creating a dichotomous key". Once they have become familiar with dichotomous keys they can go the butterfly family pages to see the characteristics of each family.

  1. To get there: Click on Atlas Home, Biology, Butterflies, and then on Family Tree.
  2. From the family tree page, just click on each of the eight families to obtain information on the families of butterflies.
  3. Emphasize to the students that they must pay careful attention to detail. Groups should use these pages to obtain defining characteristics of the families of butterflies. Use these defining characteristics to make a dichotomous key to distinguish these families.
  4. If there is time, groups should switch papers and try to follow the dichotomous keys made by other groups.

These are links to access the handouts and printable materials.
Dichotomous Key

Related Lesson Topics:
Biology: Butterflies
Biology: Biology Topics

Lesson plan by James Scannell and Stefan Sommer, 2001
Idaho Achievement Standards (as of 7/2001) met by completing this activity: