Background

You and your students may have observed that some caterpillars develop more quickly than others, or that some adults emerge from their pupae in fewer days than others. This is often due to differing temperatures in the classrooms. Development time is strongly affected by temperature; for example, caterpillars will develop more quickly in warmer conditions. On the other hand, you can actually slow development down by cooling the monarch, within certain limits. It is okay to refrigerate eggs, caterpillars and pupae for a few days, simulating what might occur on a cool fall night. For further information on the general life cycle and how long each stage typically lasts, see Background on Butterfly and Moth Life Cycles in the Monarch Biology section. Also see Monarch Butterfly Rearing and Observing Techniques in the How To section for tips on handling pupae.

Materials

• 2-4 pupae that formed on the same day
• Paper cups with crumpled Kleenex or paper towel inside (1 per pupa)
• Sewing thread to re-attach pupae to top of cage
• Individual student thermometers
• Effects of Temperature on Pupa Development Time Data Sheet (student handout page)
• Space in a refrigerator

Procedures

Guide your students through the following steps of the scientific method. They may come up with alternative hypotheses, methods, and results. Those we’ve listed here are only examples.

Question: Does temperature affect the length of time it takes for an adult to emerge from its pupa?

Hypothesis: Pupae experiencing cold conditions will take longer to develop.

Methods:

1. Start with pupae that formed on the same day, if possible. When the pupae are three days old, carefully remove them from the spot where they formed the pupa (see directions in HOW TO section of this curriculum). Place them upright in separate paper cups, cushioned by the tissue and covered with a lid. The teacher should probably do this step. If you don’t have several pupae form on the same day, do this step at the same age for each pupa, not on the same date.
2. Place a thermometer next to each pupa, as close to it as possible without touching it. Record the temperature at the same time each day for each pupa until the adults emerge.
3. Carefully place half of the cups in a refrigerator for three days. Be sure to record temperature in the refrigerator each day.
4. After three days, remove the cups from the refrigerator and carefully reattach all of the pupae to the cage (see Butterfly Rearing and Observing Techniques in the How To section). Be sure to label the pupae, recording which were refrigerated and which were not.
5. Continue to take daily temperature readings and record these readings on the graph provided.

Sample Results: The pupae kept in the refrigerator for three days took longer to develop.

Conclusions: The results indicate that monarch pupae exposed to colder temperatures take longer to develop and to emerge as adults.

Worksheets

The following are examples of the worksheets necessary for this lesson. You may print them directly from the site. If you experience problems, please email us at webadmin@monarchlab.org

• Effects of Temperature on Pupa Development Time Data Sheet
• Daily Temperature for Each Chrysalis