Monarch, Danaus plexippus, Fun Facts
A whisp of movement on a ball of bright pink flowers catches the eye. People and predators alike notice the striking orange wings outlined by black margins and white dots. This is a vision of a monarch butterfly drinking from the ever-important milkweed plant in a nearby garden.
This vision is not the only thing drawing attention to these imperiled butterflies these days. There are whispers of a possible Endangered Species Act listing floating around.
Before we take flight into why these beautiful butterflies are deserving of ESA listing, let’s answer some of the most common questions about monarchs. Read on to learn about the monarch butterfly life cycle, monarch butterfly migration and how long monarchs live.
1. The monarch butterfly life cycle occurs in four stages.
Monarch butterflies have a similar life cycle as other butterflies. They go through the infamous physical transformation known as metamorphosis over the course of four stages. The stages are egg, caterpillar, chrysalis and butterfly.
Much of the monarchs’ life cycle requires a specific range of heat and light. For monarchs, they reproduce during the summer when the temperature is between 72- and 80-degrees Fahrenheit. These butterflies will grow faster when it is hotter, or closer to 80-degrees, and have more light.
2. Females can lay up to 300 monarch butterfly eggs in her lifetime.
Monarch butterfly eggs are laid on milkweed plants, which are the sole food for monarch caterpillars. The eggs hatch an average of four days later.
3. Monarch caterpillars grow from less than a quarter of a centimeter to 4 ½ centimeters.
Monarch butterfly caterpillars shed their skin roughly five times throughout this life stage. Each time these caterpillar sheds its skin it grows and develops more into the yellow, white and black striped caterpillars many people will recognize.
When monarch caterpillars hatch, they are less than a quarter of a centimeter long and are gray with black heads. One to three days later the caterpillars shed their skin. Monarch caterpillars are now around quarter of a centimeter long and are often called “blondes” because they are light in color.
Over the next three skin sheds – which last five to 11 days – monarch caterpillars will grow from half a centimeter to 4 ½ centimeters, or just under 2 inches.
4. The monarch chrysalis is created from the caterpillar shedding its final skin.
Once monarch caterpillars are fully grown, they leave the milkweed and find a safe twig or branch to spin a silk pad. Using its cremaster, which is the stem on their bottoms, they attach to the silk pad and begin shedding their final skin. The shed reveals a light green-yellow chrysalis. As the butterfly nears emergence, its chrysalis teases the staple orange, black and white coloration.
5. Monarch butterflies are poisonous and aposematic.
Aposematism, or warning coloration, is when an animal or insect exhibits bright colors to warn predators they are poisonous. Monarch butterflies’ bright orange wings tell birds, mice, wasps and other predators to stay away.
Monarchs get their toxicity from the milkweed plants they eat as caterpillars.
6. There are two migratory populations of monarchs in North America: an eastern and western.
The eastern migratory population of monarch butterflies are found east of the Rocky Mountains. This population breeds in central and eastern U.S. and in Canada. These monarchs then migrate to Mexico for the winter.
The western migratory population of monarch butterflies are found from Northern California up to British Columbia, Canada, and east into Nevada during the summer months. For winter, this population migrates to southern California.
7. Monarch butterfly migration is carried out by generations of monarchs.
The monarch butterfly migration is over 3,000 miles long. The first three generations of monarch butterflies will live two to six weeks and will carry out the northward migration during summer. The fourth generation can live six to nine months and will migrate southward. During the winter this fourth and final general of the summer goes into dormancy.
Monarch butterfly migration is considered a great phenomenon because it is carried out by individuals who have never made the journey before by following an internal compass. Few insects make a fall migration this spectacular.
8. Monarch butterflies are in trouble, and it all comes back to milkweed.
Monarch butterflies rely on milkweed throughout their lives for food, shelter and protection. Milkweed, however, has been dramatically reduced over the past few decades. Herbicides and land cover change are the primary culprits.
This loss of milkweed sites across the United States has led to the disappearance of billions of monarchs. The International Union for Conservation of Nature lists monarch butterflies as vulnerable and their migration as a threatened phenomenon.
You can help monarchs by planting and supporting native flowering plants, including milkweed in your backyard, porch, school or business. You can also help all butterflies by eliminating your use of pesticides, which often harm these insects even though they are not the target.
Author
Allison Cook
Areas of Expertise: Communications, writing for the blog and website
Allison joined Defenders of Wildlife in 2023 after working for Smithsonian's National Zoo and Conservation
Andrew Carter
Wildlife & Wild Places
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