The monarch’s scientific appellation Danaus plexippus translates as “sleepy transformation.” This name references this butterfly’s migratory habits, coming as it does from the Greek legend of Danaus, a mythical king whose daughters fled their home country. The name “monarch” probably stems from another, older name for the insect that recognized a monarch, or regent. Perhaps because of the insects' color or majestic size, the early North American settlers referred to monarchs as “king billies,” after William of Orange, who with his wife Queen Mary ascended to the British throne in 1689.

Monarchs have a wingspan of about four inches, making them one of the largest butterflies seen in North America. Their wings are a bright red-orange color, with black veining. The wings’ margins are black and feature two series of small white spots. Male monarchs have slightly larger wings than do females. Males can also be distinguished by thinner black veining and two black dots on their hind wings.

Monarch female
Monarch male

The tiny oval eggs that the female monarch lays on the underside of a milkweed leaf are creamy white to pale yellow. After the newly hatched caterpillars eat the eggs from which they hatch, they begin munching on milkweed. Within a couple of weeks, a monarch caterpillar reaches 2 inches in length, and is recognizable by its black, yellow and white stripes. In its chrysalis stage, a monarch pupa is first blue-green. Shortly before it completes its transformation into a butterfly, the chrysalis takes on the familiar orange and black colors.

The female monarch deposits her eggs on the underside of milkweed leaves.
Monarch caterpillar feasting on milkweed.
The caterpillar assumes a "J" shape as it prepares for the chrysalis stage.

Warning Colors
During its larval stage, a monarch caterpillar ingests large quantities of poisons called cardiac glycosides from the leaves of the milkweed, with the result that predators learn to avoid the orange and black butterfly because of its toxicity. At one time scientists believed that the similar-looking viceroy butterfly mimicked the appearance of the noxious-tasting monarch to fool predators into thinking that it also tasted bad. More recent studies have shown that the monarch and viceroy are examples of something called Mullerian or mutual mimicry. Due to the salicylic acid content in their diet of willow leaves, viceroy caterpillars take on a different but equally unpalatable taste. Thus, the butterflies' resemblance to one another is of mutual benefit to both the monarch and the viceroy.

Limenitis archippus, the viceroy butterfly
The viceroy butterfly looks very similar to the monarch. Notice the black line on the hind wings, not present on the monarch.

Migratory Habits
The monarch’s yearly migration from north to south and back again is legendary, not just because of the astonishing number of miles this small insect travels, but also because the trip spans the lives of several generations of butterflies and no single monarch makes the entire round trip.

The majority of monarch butterflies live for only four or five weeks. But as autumn weather arrives in their northern habitat, monarchs have the capability to create an especially long-lived group of progeny, called the “Methuselah” generation (after the Old Testament figure with the oldest mentioned age in the bible). These particular butterflies are capable of surviving for up to seven or eight months -- long enough to make a southern migratory flight of between 1,200 and 2,800 miles to the mountains of central Mexico. Here they enter hibernation between late October and early November. As the weather warms up in the second half of February, these same butterflies mate and then begin the first leg of the long return flight north. During the two month-long migration, females lay eggs, creating successive generations who will complete the spring trek north until the butterflies reach their reproductive grounds in North America, as far north as southern Canada.

Monarch migration
Monarch sanctuary in Michoacan, Mexico

Reduced Numbers
Human development, herbicide use and the production of genetically modified crops have all contributed to habitat loss for the monarch, according to Chip Taylor, director of Monarch Watch, a monarch conservation group. The group has initiated a nationwide landscape restoration project called “Bring Back the Monarchs.” The World Wildlife Fund is also active in protecting and restoring the monarch butterfly by preserving the Mexican pine and fir forest that is the insects’ winter habitat.


The Asclepias genus, or the milkweeds, contains over 100 species. Because certain milkweeds have a long history of use as a folk medicine, Linnaeus named the genus after Asclepius, the Greek god of healing. The common name milkweed derives from the white sap released whenever the plant’s stems or leaves are cut or broken. The milky white juice of Asclepias plants contains alkaloids that are poisonous to vertebrates such as cattle, sheep and horses. These plant toxins are beneficial to monarch larvae, however. After ingesting the milkweed’s leaves, both the monarch larvae and adult butterflies become distasteful to predators such as birds.

Some of the more common North American milkweeds are:

A. syriaca, the common milkweed (zones 4-9), grows to 3 to 4 feet and is native to most of North America east of the Rockies. This pink-flowered species is commonly seen growing in fields and along roadsides. Its deep roots can cause it to become invasive in a garden setting.

A. incarnata
, the swamp milkweed (zones 3-8), reaches from 3 to 6 feet in height and has narrower leaves than that of the common milkweed. It is native to most of the U.S. and eastern Canada. This plant prefers heavy, wet soil in a full sun location. Among the swamp milkweed’s numerous cultivars are 'Ice Ballet,' 'Soulmate' and 'Cinderella.'

A. tuberosa
or the butterfly weed is native to most of the U.S. and eastern Canada. This showy orange-flowered species makes an attractive addition to any sunny border. Butterfly weed reaches from 1 to 3 feet high and is a popular nectar plant for many other butterflies besides the monarch.

A. speciosa, showy milkweed (zones 3-9), reaches 3 to 4 feet high and grows in the western half of the continent. Its pink and white flowers are fragrant, like others in the milkweed family. Native Americans used this some parts of this plant for medicine and even for food.

A. curassavica, the Mexican or tropical milkweed, is perennial in zones 9 and 10 only, but can be grown as an annual in colder climates. Its beautiful flowers are a mixture of orange and bright red.

A. variegata or white milkweed (zone 4 and warmer) is native to eastern North America. It grows in lean soil and unlike others of the genus, likes shade. Its other name, redring milkweed, comes from the maroon-colored ring at the base of each flower.
A. syriaca, common milkweed
A. incarnata, swamp milkweed
A. tuberosa, butterfly weed
A. speciosa, showy milkweed
A.curassavica, Mexican milkweed
A. variegata, white milkweed

Seed Pods
The common milkweed becomes especially noticeable in the fall when its 2- to 4-inch-long bumpy green pods turn brown and burst open, dispelling hundreds of seeds borne on the wind by downy fluff. The empty dried pods are decorative in their own right and have served as the basis of many a craft project.

Role in Nature
The asclepias genus is vital to the survival of the monarch, since it is the exclusive host plant for larvae of this beautiful butterfly. But milkweed plants provide habitat for numerous other creatures as well. Not just the monarch, but other butterflies such as the painted lady, mourning cloak and eastern black swallowtail take nourishment from milkweed flower nectar. The honeybee and the ruby-throated hummingbird also rely on the blossoms as a food source. Common milkweed serves as a hiding place for insects such as spiders and wasps, and provides shelter for many other creatures like the chickadee, goldfinch and white-footed mouse.

The bast, or inner bark, fiber of the milkweed is strong as well as soft, and was used by Native Americans to make string or rope. The silky floss inside the seed pods is an excellent insulator, and was stuffed into life jackets during World War II. American pioneers used the plant’s white sap as a treatment for warts, and the dried seed pods as Christmas ornaments.

Attracting Monarchs To Your Yard

If you wish to attract monarchs to your yard, you will certainly want to provide milkweed as a host plant for the butterflies’ larvae. If you have enough room, plant several different species of milkweed. Common milkweed is a butterfly favorite, but if your space is limited, you may want to plant it in a pot to contain its aggressive roots. The better-behaved swamp milkweed will grow even in drier situations. A. tuberosa, the butterfly weed, and A. curassavica, the Mexican milkweed, offer the most colorful flowers.

Your garden most likely already contains a number of the plants whose nectar the monarch enjoys. If you don’t already grow them, consider adding annuals such as the zinnia, verbena, cleome and salvia. Good perennial sources of nectar include the phlox, monarda, sedum, aster, coreopsis, joe pye weed, liatris and buddleia. All butterfly gardeners should avoid the indiscriminate use of pesticides. You can register and certify your property as a monarch waystation habitat at


World Wildlife Fund: Monarch Butterflies
Talking Science: Mutual Mimicry
Monarch Watch: Milkweed
The Wildlife Porch: Milkweed
JoyfulButterfly: Milkweed Plant for Monarchs
Monarch Watch: Butterfly Gardening

Photo credits:
Thumbnail photo and male and female monarchs by TexasEagle
Monarch egg by Anita 363
Caterpillar by cupprof
Chrysalis by N8ure Lover
Viceroy by gurdonark
Monarch migration by farflungphotos
Monarch Mexican sanctuary by Aviruthia
Monarch on milkweed flowers by SidPix
Field of milkweeds by Salim Virji
Milkweed pods by keithcarver
Monarch on zinnia by 3PandQ

Thanks to DG photographers:
A. syriaca by poppysue
A. incarnata by poppysue
A. tuberosa by poppysue
A. speciosa by AnniesAnnuals
A. curassavica by Marilynbeth
A. variegata by sladeofsky