Monarchs are a familiar butterfly to all, from kids to grandparents. With a wingspan of nearly 4 inches and easily recognized by the black, orange and white pattern, monarchs are unique in the butterfly world.

The monarch's life cycle is especially fascinating. However, the monarch population is declining and scientists are concerned if actions aren't taken to reverse the decline, monarchs may disappear forever.


First, let's explore why monarchs are so captivating.

group of monarchs clustered on branch
  • The eastern population of monarchs overwinter at the Monarch Butterfly Biosphere Reserve, a rugged forested mountain area in Mexico about 60 miles northwest of Mexico City.
  • These adults migrated up to 3,000 miles from the northern United States and Canada the previous fall.
  • From November to March, they cluster together on trees to stay warm, sometimes by the tens of thousands on a single tree.

Annual Migration/Reproduction Cycle
(North Dakota to Mexico Migrants)

Wintering Grounds: The Monarch Butterfly Biosphere Reserve.

Migration map wintering grounds

Early April: Migrating monarchs reproduce creating Generation 1.

Migration map generation 1

Late May: Generation 1 reproduces.

Migration map generation 1 reproduction area

June: Generation 2 reproduces.

Migration map generation 2 reproduction area

July - August: Generation 3 reproduces.

Migration map generation 3 reproduction area

September - October: Adults from gen. 3 and 4 migrate south to the overwintering grounds in Mexico.

Migration map generation 3 and 4 moving south to Mexico wintering grounds
Generation 1 graphic
  • Generation 1: The adults that overwinter in Mexico leave the reserve in March and head north to Texas and the southern United States, mate and lay eggs, and it is these offspring that continue the journey north as adults. Consider these the Generation 1 monarchs, or the children of the monarchs that overwintered.

    The Generation 1 adult monarchs continue moving north to the Corn Belt states and all over the eastern U.S., with some reaching North Dakota in late May.

Breeding Cycle

Now that the monarchs are in North Dakota, let's go over the breeding cycle. Female monarchs only lay eggs on milkweed species. In North Dakota, the primary milkweed species they seek are common milkweed and showy milkweed, which are both native wildflowers in the state. Butterflies undergo complete metamorphosis, in which there are four distinct stages: egg, larva (caterpillar), pupa (chrysalis) and adult.

Showy and Common Milkweed

Now that the monarchs are in North Dakota, let's go over the breeding cycle. Female monarchs only lay eggs on milkweed species. In North Dakota, the primary milkweed species they seek are common milkweed and showy milkweed, which are both native wildflowers in the state. Butterflies undergo complete metamorphosis, in which there are four distinct stages: egg, larva (caterpillar), pupa (chrysalis) and adult.

Female monarchs lay one egg per milkweed plant and in her lifetime she will lay hundreds of eggs. The eggs hatch after a few days and a tiny caterpillar emerges. The caterpillar immediately starts eating the milkweed leaves, and continues to eat, and eat, and eat.

Caterpillar Stages

As the caterpillar grows it becomes too large for its skin, so it “molts,” or sheds its skin, which it often eats, too. It goes through 5 stages of molts, which are called instars. The entire caterpillar stage lasts 9-14 days. During this time, they grow nearly 10 times in size, from 4-45mm.

When the caterpillar is ready to pupate (change into a chrysalis), they spin a silk mat and attach their rear end to it, and hang in a “J” formation. Watch closely … soon the caterpillar splits its skin, wiggles out, and now it is a chrysalis. Note that butterflies do no spin a silken cocoon like moths, to call a butterfly pupa a cocoon is incorrect.

For the next 8-15 days, changes are happening in the chrysalis. Wings and adult organs are forming. Just before the monarch is ready to emerge, the black, orange and white wing patterns are visible through the pupa covering. The chrysalis splits, the adult monarch.

Generation 2 graphic
  • Generation 2: So now it's late May in North Dakota, and the Generation 1 adults have mated and laid eggs. These offspring are Generation 2 and are the grandchildren of the overwintering monarchs. They will become adults sometime in June, mate and reproduce, and their offspring are Generation 3, or the great-grandchildren of the overwintering monarchs.
Generation 3 graphic
  • Generation 3: In late July and August, the Generation 3 adults have mated and produced Generation 4. These are the great-great grandchildren of the overwintering monarchs.
Generation 4 graphic
  • Generation 4: The Generation 4 monarchs enter a state of reproductive diapause, meaning their reproductive organs remain in an immature state so they do not reproduce. Somehow, these monarchs, which are 4 generations removed from their ancestors, migrate in September and October from northern breeding grounds, all to the same forest reserve in Mexico where they've never been before. The same place that their great-great grandparents left 6-7 months ago.

     

It's an amazing process in nature that is teetering on the edge of extinction. The monarch population has declined from a high of almost 1 billion monarchs in 1996 to a low of 35 million in 2013. There many factors that contribute to the decline: disease, illegal logging in the Mexican wintering grounds and predation. However, the primary concern is loss of habitat, such as CRP and native prairie, where monarchs can find both milkweed for the caterpillars and adult nectar food sources.

Because of the decline, the monarch has been petitioned to be listed under the Endangered Species Act. The monarch is a species that every citizen can help bring back, from planting backyard butterfly gardens, to leaving some roadside patches of milkweed unmowed, to keeping CRP on the landscape. Find out more about monarchs, other pollinators, and how you can help at https://gf.nd.gov/wildlife/pollinators