Wikijunior:Bugs/Monarch butterfly

What does it look like?
The name Monarch means “king”. An adult Monarch Butterfly is about 1 ½ inches long. Its body is black with white markings. There are white spots on the head and around the wing edges. The wings are bright orange with black veins. The undersides of the wings are light orange. Male Monarchs have a black spot on the back of each hind wing.

Wings have 2 parts: a forewing and a hind wing. The wing span can be up to 4 inches across. The back edges of the wings are called “margins”. They bend to push air backward and move the butterfly forward. The stiff front edges of the wings lift the butterfly in flight. Black veins create a framework that keeps the wings stable. Female wing veins are thicker than those of males.

Monarch Butterflies come from yellow, black, and white striped caterpillars. Monarch caterpillars grow to about 2 inches in length. They have 2 tentacles that look like antennae at the front of the body, and 2 tentacles at the back.

Where does it live?
One population of Monarch Butterflies lives on the eastern side of the Rocky Mountains. In the fall, the eastern population migrates to the cool mountains of central Mexico. They overwinter on just twelve isolated mountaintops in the Oyamel Forest.

When spring arrives, the eastern Monarchs leave Mexico. They fly north through Texas and the Midwestern plains. Finally, they reach the Great Lakes region. By late summer, they will have spread to Canada and the east coast of the United States.

Another population of Monarchs lives on the western side of the Rockies. The western Monarchs spend the winter on the warm California coast. They like the moderate temperatures. They overwinter by clustering in groves of trees. The groves are scattered along the coast from Mendocino County in northern California to Baja in southern California.

In the spring, adults begin to move inland. They feed on flower nectar. They mate and lay eggs on milkweed plants. When they die their offspring repeat the cycle. Several generations later, the last adults produced in late summer and fall migrate to the coast. The new Monarchs have never been there before, but they can find their way to the same groves used by previous generations.

What does it eat?
Monarch caterpillars feed on plants of the milkweed family. Adult Monarchs drink the nectar of milkweed flowers. They also like joe-pye weed, New England aster, purple coneflower, and false blue indigo.

How does it defend itself?
Monarch Butterflies use 2 methods of self defense: warning colors and poison. Milkweed plants that Monarch caterpillars eat are poisonous. The poison does not hurt the caterpillars. The poison stays inside as they turn into adults. The bright colors of both caterpillar and adult butterfly warn predators to stay away. Birds and other predators will not eat them. The amount of poison decreases as the butterfly gets older. Males have less of the poison than females.

What stages of metamorphosis does it go through?
Monarch Butterflies undergo complete metamorphosis. They go through 4 stages in a life cycle: egg, caterpillar (larvae), pupa (chrysalis), and adult. They make 4 generations in one year.

Females lay hundreds of tiny white eggs on the underside of milkweed leaves. In 3 to 5 days the caterpillar chews its way out of the egg shell. Then it eats the broken shell for nourishment. The caterpillar moves away from the leaves where the eggs were laid. It feeds on the leaves of the milkweed plant.

As a Monarch caterpillar grows, the skin gets too tight and splits open. This happens several times. When the skin splits for the last time, the caterpillar makes a protective covering (chrysalis). It finds a twig or branch and attaches itself with its back legs. Hanging upside down, it weaves the chrysalis, starting from head at the bottom to back end at the top. The chrysalis is finished when it reaches the legs attached to the branch. Inside the chrysalis, the Monarch enters its resting stage.

The Monarch chrysalis is light green with tiny yellow spots along the edge. Inside the chrysalis, the caterpillar changes into a winged adult butterfly. When ready, the chrysalis splits open and the adult butterfly pulls itself out. The new wings are crumpled and wet. The butterfly rests in the sun until the wings flatten and dry. Adults do not mate right away. Instead they fly to the Oyamel forest in the mountains of Mexico. The Monarchs cluster together on trees for protection. They hibernate until spring when it is time to mate. In February and March, the final generation of Monarch butterflies comes out of hibernation to mate. They migrate north and east in order to find a place to lay their eggs. This starts a new “1st” generation.

The first 3 generations usually die about six weeks after mating. The 4th generation is called the Methuselah (long-living) generation.

What special behavior does it exhibit?
The male Monarch has a black spot on each hind wing. The spots are glands that make a special scent to attract females.

To sip nectar from a flower the adult butterfly has a spiral, straw-like tongue (proboscis). The tongue rolls out to drink, then rolls up out of the way. The tongue works like a paper towel with tiny grooves that soak up drops of nectar.

Monarchs travel alone in daylight. They cluster on tree trunks at night. A cluster of butterflies is called a “roost” or a “bivouac”. Some roosts are small with just a few butterflies. Others roosts can harbor thousands of butterflies.

How does this bug affect people?
Monarch Butterflies are not considered pests. They benefit people by pollinating plants. They prefer native plants, especially milkweed. People like native plants because they are hardy and need less water and fertilizer. Native plants attract butterflies to gardens.

Monarch Butterflies are adapted to the delicate environment of the Oyamel Forest in Mexico. To protect the habitat, the Mexican government has created the Oyamel Forest Monarch Butterfly Preserve. They have made laws against cutting down the trees in the Oyamel Forest.

Monarch Butterflies are important pollinators. Pollinators help plants reproduce and create food for people.

Monarch populations have declined over the last 20 years because of lost habitat in many areas. Pesticide exposure and climate change have also caused harm. There are many Monarch conservation projects throughout the United States.