Monarch Butterfly Life Cycle: What is a Generation?

The monarch butterfly life cycle goes from egg to larva to chrysalis to adult. During the breeding season, this cycle repeats itself over and over. Each complete cycle is called a “generation.”

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Egg Larva Chrysalis Adult
Monarch Life Cycle
Insects have very short generations. A monarch generation takes about one month to develop, depending on temperatures. (Fruit flies complete their full life cycle in less than two weeks! This is why they are so useful to scientists who study genetics.)
Try This!  

How many generations do you see?

How Long Are Other Animal Generations?
How long are Bald Eagle generations? How about Manatees and Gray Whales? To find out, you need to know the age of an animal when it first reproduces. You can find this information for each animal in the FAQ section of the Journey North website.

How Long Are Human Generations?
Four human generations are pictured here. Can you find the child, parent, grandparent and great-grandparent? These familiar names are used when we talk about generations. They describe the relationships between generations.

How long are human generations? Draw your family tree (children, parents, and grandparents is enough). Record the year each person was born in each generation. Next, go back and calculate the age of each person when their first child was born. Finally, calculate the average age at which each generation produced their first child. Back at school, compare the length of generations for the families in your class.

Journaling Questions
  • According to your class averages, how long is a human generation?
  • Are the generations the same length now as they were for your grandparents? Discuss possible reasons for any differences you see.
  • What similarities and differences do you see between animals with short and long generations?

National Science Education Standards

Life Science
Plants and animals have life cycles that include being born, developing into adults, reproducing, and eventually dying. The details of this life cycle are different for different organisms. (K-4)

Reproduction is a characteristic of all living systems; because no individual organism lives forever, reproduction is essential to the continuation of every species. (5-8)

National Math Standards

Problem Solving
Solve problems that arise in mathematics and in other contexts.

Number and Operations
Compute fluently and make reasonable estimates.