Monarch butterfly

The **monarch** butterfly (*Danaus plexippus*) is an insect in the Nymphalidae family. It is the best-known butterfly in North America.

Monarchs are known for their long  migrations. In North America, they travel long distances south in the fall, and north in the spring.  They start to migrate south in about August. They must get to frost-free areas. Freezing will kill them. A migration towards the north starts in the spring.

No single  makes the whole round trip.  The migration north spans the life of three to four generations of the butterfly. A longer-lived "super generation" flies from the northern-most parts of the butterfly's range in Canada all the way to Mexico. It overwinters in the south, and breeds in the spring to start the next generation flying north. The following reference gives a map of the migration routes.

## Description
### Caterpillar 
The monarch caterpillar is banded with yellow, black, and white . The head is also striped with yellow and black. There are four black body , two on each end of the body. They look similar to antennae. The caterpillar will be as long as 5&nbsp;cm (2&nbsp;inches).

### Adults 
The monarch butterfly has a wingspan that ranges from 8.9 to 10.2 centimeters (3½ to 4&nbsp;inches).

The upper side of the wings are orange with black edges and veins. There are white spots in the black wing margins. The male has a spot on his bottom wing. The spot gives out scents which  females. It was named *nivosus* by lepidopterists (a lepidopterist is a person who studies butterflies and moths). It is grayish white in all areas of the wings that are normally orange. The white form makes up about 1% or less of all monarchs except for on Oahu, Hawaii where it has kept  as high as 10%. The existence of two or more forms of a species in the same area is quite common, and is called polymorphism.

## Range and distribution
In North America, the monarch is found from  Canada to  South America. It sometimes wanders to western Europe, sometimes as far as Greece. It reaches Europe from being transported by USA ships. It can also wander to Europe by flying there if weather and wind conditions are right. It has also been found in Bermuda, Hawaii, the Solomons, New Caledonia, New Zealand, Australia, New Guinea, Ceylon, India, the Azores, and the Canary Islands.

### Migration
Monarch butterflies are known for their long annual migration. In North America, they make large migrations towards the south starting in August until the first frost. A migration towards the north takes place in the spring. No single  makes the whole round trip. Female monarchs lay eggs for the next generation during these migrations. They migrate to the sanctuaries of the Mariposa Monarca Biosphere Reserve in the Mexican states of Michoacán and Mexico. Most of the monarchs that are west of the Rocky Mountains do not travel all the way down to Mexico. Instead, they overwinter (spend the winter) in many places in central and southern California.

While in Mexico, the monarchs gather in very large numbers to rest. They perch on suitable trees and bushes by clinging (hold on to tightly) with their feet. They cling to each other making layers and layers of resting Monarchs overwintering. This was discovered by Fred Urquhart of the University of Toronto, who studied monarch butterflies for nearly forty years. He knew the Monarchs migrated because he would stop seeing them after a certain time of the year. He put a  on each Monarch he found. On this label was his name, address, and a request to send him the butterfly if it was found.

A few months later, people from all over North America and Mexico began  his labelled butterflies to him. Mexico was the southernmost area from which he had received a butterfly, so he started traveling there to look for the Monarchs. For many years, he traveled to Mexico. There he  through jungles, walked through forests, and talked to the people he found. He  heard there was a place west of Mexico City where people had seen lots of monarchs all together. After a long search, He finally found millions of monarch butterflies covering every part of the area. The monarch can be found in almost any kind of habitat during migration. It overwinters in pine, cypress, and eucalyptus  in California.

Much of the monarch's breeding habitat is not good . In some states and provinces, milkweed is thought to be a weed. In these places, the milkweed is killed to keep livestock from eating it and becoming sick. Moreover, herbicides use, especially with genetically modified herbicide-resistant plants, eliminate milkweed. With fewer milkweed plants, the monarch does not have as much habitat to breed in.

Habitat destruction has been a concern as the number of monarch butterflies that completed an annual migration to their winter home in a Mexican forest sank in 2013 to its lowest level in at least two decades, due mostly to extreme weather and changed farming practices in North America. The Mexican forest occupied by the butterflies, once as high at , dwindled to  in the annual census conducted December 2012.

## Life cycle
The monarch butterfly goes through complete metamorphosis.

### Egg
The female lays her eggs one by one. They are  on the underside of the leaves of caterpillar's food plant. The eggs are light yellow. It is about 1.2 millimeters long. Its diameter is about 0.87&nbsp;millimeters (average on 55 eggs). The chemical slows the heart-beat of vertebrates.

When the monarch becomes a butterfly, it no longer eats milkweed, but it still has the chemical in its body. The butterfly shows that they are not good to eat with their bright orange and black wings. This is warning coloration. A bird may try to eat a monarch, but it will become sick and  after eating it. After this , the bird learns not to eat another monarch, and also any other butterfly which is similar in appearance. The viceroy is similar looking to the monarch, but does not have the milkweed poison in its body. Birds that have had the bad experience of eating a monarch will usually not eat a viceroy. It is an example of Müllerian mimicry.

## Threats
### Predators
Overwintering Monarchs in Mexico are often eaten by black-headed grosbeaks. These birds are immune to the glycoside. Other birds, such as orioles and jays, have learned to eat only the thoracic muscles and the body parts inside the abdomen. These parts have less poison than the rest of the body.

### Parasites
Parasites include the tachinid flies *Sturmia convergens* and *Lesperia archippivora*. Caterpillars that have the *Lesperia archippivora* maggots inside them will finish their last molt. They will then hang upside down on a  surface. They die before they turn into a chrysalis. At that time one white maggot comes out of the caterpillar. The maggot then forms a brown pupa on the ground.

The bacteria *Micrococcus flacidifex danai* also infects the caterpillar and causes “black death”. Just before turning into a chrysalis, the caterpillar will find a horizontal surface. They die a few hours later. The body turns black shortly after. The bacteria *Pseudomonas aeruginosa* causes infections in weakened insects. It is a common cause of death in insects that are  in laboratories. Idaho, Illinois, Minnesota, and Texas. It is the state butterfly of
Vermont and West Virginia.
It was  in 1990 as the national insect of the United States of America. It was nominated along with the honeybee (*Apis mellifera*). However, the legislation did not pass.

Many people like to attract monarchs by growing a butterfly garden with the plant *Asclepias physocarpa*. Others like raising them for fun or for educational purposes.  have been made for migrating Monarchs. The sanctuaries are found at the monarch's  overwintering places. These migrations can create a lot of tourism revenue.

Many schools also enjoy caring for monarchs. They start with caterpillars. When the caterpillars  into butterflies, they are then set free into the wild.

Some organizations, such as the Cape May Bird Observatory, have monarch labeling programs. Labels are placed on the wing of the butterfly. The labels have information on them. This helps scientists  the monarchs during their migration. It also helps the scientists study the  that the monarchs take on their migration.

## Adult food sources
Adult Monarchs have been seen on a number of different nectar plants.  Here is a list of some of them:

* *Apocynum cannabinum* – Indian hemp
* *Asclepias incarnata* – Swamp milkweed
* *Asclepias syriaca* – Common milkweed
* *Asclepias tuberosa* – Butterfly weed
* *Aster* sp. – asters
* *Cirsium* sp. – thistles
* *Conyza canadensis* – Canadian horseweed
* *Daucus carota* – Wild carrot
* *Dipsacus fullonum* – Fuller's teasel

* *Eupatorium perfoliatum* – Common boneset
* *Eutrochium maculatum* – Spotted joe-pye weed
* *Hesperis matronalis* – Dame's rocket
* *Medicago sativa* – Alfalfa
* *Solidago* sp. – golden rods
* *Syringa vulgaris* – Lilac
* *Trifolium pratense* – Red clover
* *Vernonia gigantea* – Tall ironweed

Males will also take in water and minerals from damp soil and small, wet rocks.  This is known as *puddling*.  The Monarch has also been seen puddling at an oil stain on pavement.

## Food plants
Here is a list of plants that the Monarch caterpillar eats:

* *Asclepias amplexicaulis* – Clasping milkweed
* *Asclepias asperula* – Antelope horns
* *Asclepias californica* – California milkweed
* *Asclepias cordifolia* – Heart-leaf milkweed
* *Asclepias curassavica* – Scarlet milkweed
* *Asclepias curtissii* – Curtiss' milkweed
* *Asclepias eriocarpa* – Woollypod milkweed
* *Asclepias erosa* – Desert milkweed
* *Asclepias exaltata* – Poke milkweed
* *Asclepias fascicularis* – Narrow-leaf milkweed
* *Asclepias humistrata* – Sandhill milkweed
* *Asclepias incarnata* – Swamp milkweed

* *Asclepias nivea* – Caribbean milkweed
* *Asclepias physocarpa* – Swan plant
* *Asclepias purpurascens* – Purple milkweed
* *Asclepias speciosa* – Showy milkweed
* *Asclepias subverticillata* – Horsetail milkweed
* *Asclepias syriaca* – Common milkweed
* *Asclepias tuberosa* – Butterfly weed
* *Asclepias verticillata* – Whorled milkweed
* *Calotropis gigantea* – Crown flower
* *Calotropis procera* – Apple of Sodom
* *Cynanchum laeve* – Sand vine
* *Sarcostemma clausum* – White vine

## References