Range: The monarch butterfly is native to North, Central, and northern South America. It has been accidentally introduced to numerous islands in the pacific and Atlantic.
Habitat: In the spring and mid-summer, the monarch butterfly’s habitat is open fields with milkweed. In the fall, monarchs seek forested areas with a specific microclimate – overnight temperatures above freezing but cool in the daytime.
Food: Monarch butterfly larvae feed on milkweed. Adults gather nectar from flowers. Because most milkweeds contain bad tasting chemicals (glycosides) that are incorporated into the adult, monarchs are distasteful to predators.
The monarch life cycle
Egg: The female monarch will only lay her eggs on milkweed plants. She will lay hundreds of eggs, but scatters them on many plants to increase their chances of survival. They are usually laid on the underside of a milkweed leaf. The egg hatches after three or four days.
Larva (Caterpillar): The first thing the larva does is eat its own eggshell. Then it begins to devour milkweed leaves. For two weeks the larva eats voraciously, shedding its skin four times and growing to about 2 inches in length. The larva then attaches itself to a suitable location and forms a “J.”
Pupa (Chrysalis): The skin of the caterpillar splits and peels off, revealing a beautiful green chrysalis. The chrysalis stage lasts for around two weeks as an adult butterfly develops inside.
Adult: The adult butterfly emerges from the chrysalis. It inflates and dries its wings, then takes off and begins searching for nectar. Adults live for 4-6 weeks during which time they mate and females lay eggs.
Male or Female?
The male monarch has thin veins on its lower wings with a pronounced black spot.
The female monarch has thicker veins and no black spot.
The monarch migration
Unlike most other insects in temperate climates, Monarch butterflies cannot survive a long cold winter. Instead, they spend the winter in roosting spots. Monarchs west of the Rocky Mountains travel to small groves of trees along the California coast. Those east of the Rocky Mountains fly farther south to the forests high in the mountains of Mexico. The monarch’s migration is driven by seasonal changes. Daylength and temperature changes influence the movement of the Monarch.
In all the world, no butterflies migrate like the Monarchs of North America. They travel much farther than all other tropical butterflies, up to three thousand miles. They are the only butterflies to make such a long, two way migration every year. Amazingly, they fly in masses to the same winter roosts, often to the exact same trees. Their migration is more the type we expect from birds or whales. However, unlike birds and whales, individuals only make the round-trip once. It is their children’s grandchildren that return south the following fall.
Some other species of Lepidoptera (butterflies and moths) travel long distances, but they generally go in one direction only, often following food. This one-way movement is properly called emigration. In tropical lands, butterflies do migrate back and forth as the seasons change. At the beginning of the dry season, the food plants shrivel and the butterflies leave to find a moister climate. When the rains arrive, the food plants grow back and the butterflies return.
When the late summer and early fall Monarchs emerge from their pupae, or chrysalides, they are biologically and behaviorally different from those emerging in the summer. The shorter days and cooler air of late summer trigger changes. In Iowa this occurs around the end of August. These Monarchs are called the “super generation” and live for around 9 months. Even though these butterflies look like summer adults, they won’t mate or lay eggs until the following spring. Instead, their small bodies prepare for a strenuous flight. Otherwise solitary animals, they often cluster at night while moving ever southward. If they linger too long, they won’t be able to make the journey; because they are cold-blooded, they are unable to fly in cold weather.
Fat, stored in the abdomen, is a critical element of their survival for the winter. This fat not only fuels their flight of one to three thousand miles, but must last until the next spring when they begin the flight back north. As they migrate southwards, Monarchs stop to nectar, and they actually gain weight during the trip! Some researchers think that Monarchs conserve their “fuel” in flight by gliding on air currents as they travel south. This is an area of great interest for researchers; there are many unanswered questions about how these small organisms are able to travel so far.
Another unsolved mystery is how Monarchs find the overwintering sites each year. Somehow they know their way, even though the butterflies returning to Mexico or California each fall are the great-great-grandchildren of the butterflies that left the previous spring. No one knows exactly how their homing system works; it is another of the many unanswered questions in the butterfly world.
Monarch Watch at the University of Kansas oversees monarch tagging in the eastern United States. The purpose of monarch tagging is to learn all we can about this amazing butterfly. What migration pathways do they take? How does the weather influence their migration? What is their survival rate? Only through the cooperative efforts of volunteer taggers will we be able to obtain sufficient recoveries and observations of the migration to answer these questions.
Monarch tags are basically tiny stickers with a tag code (three letters and three numbers). Tagging occurs only during the monarch migration in the fall. Tagged monarchs that are recovered are listed on Monarch Watch’s website: www.monarchwatch.org.
Tagging monarchs is a great activity for people of all ages and is another way we can all contribute to monarch butterfly conservation.
To learn more about tagging, and to purchase tags, visit: www.monarchwatch.org