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How you use this lesson depends on the number and source of monarchs that you have in your classroom. You may collect larvae from the wild, collect a wild female and rear her eggs, or receive larvae from a monarch supplier. If you can collect larvae of different stages from the wild, you can do an experiment to compare rates and causes of mortality of larvae collected at different stages. You can also compare larvae you purchase to those you find in the wild or raise from eggs. Before doing this lesson, read about Predators, Parasitoids and Pathogens.

Materials

• Larva cages (enough to keep each source of larvae separate)
• Rearing supplies
• Monarch Mortality Data Table (use student handout pages, or make your own)
• Student journals, if desired

Procedure

1. Collect monarch larvae from as many sources as possible.
2. Keep records on the mortality data sheet provided.  Depending on your situation either divide the class into groups to record the necessary data for separate batches of larvae, or keep one data sheet for the whole class.
3. Each population (source) of larvae must be kept in a different cage. These cages should be the same size and kept in the same location in your classroom. Keep the same number of larvae in each cage, if possible. If you collect different stages of larvae from the wild, keep these in separate containers.
4. Give each population the same amount of milkweed (same size and number of leaves).
5. Observe each population on a daily basis and record the stage at which any die (what larval instar, pupa, or adult). If a pupa remains dark for over 2 days, it is probably dead. 
6. Keep making observations and recording data until all of the adults emerge and can fly.
7. Summarize the information from the section on Predation, Parasites and Disease. Ask students to theorize what might have caused any deaths. Have them examine the dead specimens and write their observations and hypotheses in their journals.
8. Keep dead monarchs in separate covered containers and have students continue to monitor them daily, writing in their journals. If a larva or pupa was parasitized by a fly, tiny white maggots will crawl out and change into little, dark brown pupa cases. After a week or two, flies will emerge from the pupa cases. If the cause of death was a virus, the specimen will be black and full of a foul smelling liquid.
9. Have students compare their results with their hypotheses and write conclusions in their journals.
10. If other classrooms in your school are raising monarchs, compare your mortality rates to theirs.

Extensions

1. Figure mortality and survival rates at each stage of development, and compare these for monarchs from different sources.
2. Compare causes of mortality at different stages and for larvae from different sources.
3. If you live in an area where monarchs are abundant as eggs or larvae during the school year, study mortality by tracking individual eggs and larvae on marked milkweed plants. This would be most successful if you put net screen around the larvae to keep them from crawling off the marked plant, but this method would also keep out some predators. If you come up with a good way to study mortality in the wild, let us know!

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

• Monarch Mortality Data Table Page 1
• Monarch Mortality Data Table Page 2
  

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ã 2001 Monarchs in the Classroom  - University of Minnesota
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