The Monarch is a milkweed butterfly and the most popular in North America. The wings feature an easily recognizable orange and black pattern, with a wingspan of 3.5 to 4" (8.9 to 10.2 cm), the male is slightly larger. Like all insects, the Monarch has six legs, but uses the four hind legs as it carries its two front legs against its body.
Wing size and shape differ between migratory and non-migratory Monarchs. The ones from the eastern population of North America have larger and more angular forewings than those in the western population. The Viceroy butterfly appears similar in color and pattern, but is markedly smaller and has an extra black stripe across the hind wing. (The three photos below were taken in August, 2018 on our property).
Range
The eastern North American Monarch population is notable for its annual southward, late-summer/autumn migration from the United States and southern Canada to Mexico. During the fall migration, it covers thousands of miles, with a multi-generational return north. The western North American population of Monarchs west of the Rocky Mountains mostly migrate to sites in California but have been found in Mexico overwintering sites.
Eggs
The eggs are derived from materials ingested as larvae received from males during mating. Eggs are laid individually on the underside of a young leaf of a milkweed plant during the spring and summer months. The eggs are cream-colored or light green. Though each egg is 1/1000th the mass of the female, she may lay up to her own mass in eggs. Females lay smaller eggs as they age. The number of eggs laid by a female, who may mate several times, ranges from 290 to 1180. Females lay their eggs on milkweed that make their offspring less sick. Eggs take three to eight days to develop and hatch into larva or caterpillars.
Larvae
The caterpillar goes through five major, distinct stages of growth and after each one, it molts. Each caterpillar, or instar that molts is larger than the previous as it eats and stores energy in the form of fat and nutrients to carry it through the non-feeding pupal stage.
The first instar larva caterpillar that emerges out of the egg is pale green and translucent. It lacks banding coloration or tentacles. The caterpillar eats its egg case and begins to feed on milkweed.
The second instar larva develops a characteristic pattern of white, yellow and black transverse bands. It is no longer translucent but is covered in short setae (hairs attached to nerve cells that sense touch).
The third instar larva has more distinct bands and the two pairs of tentacles become longer. Legs on the thorax differentiate into a smaller pair near the head and larger pairs further back. These third stage caterpillars began to eat along the leaf edges.
The fourth instar has a different banding pattern. It develops white spots on the pro-legs near the back of the caterpillar.
The fifth instar larva has a more complex banding pattern and white dots on the pro-legs, with front legs that are small and very close to the head.
At this stage of development, it is relatively large compared to the earlier instars. The caterpillar completes its growth. Fifth instar larvae can increase 2000 times in weight from first instars. Fifth-stage instar larva chew through the milkweed leaves and stop the flow of latex. After this, they eat more leaf tissue. Before pupation, larva must consume milkweed to increase their mass prior to pupation. Larva stop feeding and search for a pupation site. The caterpillar attaches itself securely to a horizontal surface, using a silk pad. At this point, it latches on with its hind legs and hangs down. It then molts into an opaque, blue-green chrysalis with small gold dots. It normally matures within two weeks. At this point the Monarch's characteristic orange and black wings become visible. The adult then emerges, dries its wings and flies away. From egg to adult stage will take as little as 25 days during the warm summer temperatures. During cool spring conditions this could take as many as seven weeks. During the development, both larva and their milkweed hosts are vulnerable to weather extremes, predators, parasites and diseases. Commonly, fewer than 10% of Monarch eggs and caterpillars survive. (The photos below show the egg, caterpillar and the pupae).
Adult
While the Monarch is waiting for its wings to dry, fluids are pumped into wings, they expand and stiffen. The Monarch expands and retracts its wings, once conditions allow, it flies to feed on a variety of nectar plants. During the breeding season adults reach sexual maturity in four or five days. However, the migrating generation will not reach maturity until overwintering is complete. Monarchs typically live two to six weeks during the breeding season, with an exception of the migrating generation. Larvae growing in high densities (populations) are smaller, have lower survival, and weigh less as adults compared to lower densities.
Reproduction
Males that are fit are more likely to mate. Females and males typically mate more than once, females that mate several times lay more eggs. Mating for the overwintering populations occurs in the spring, prior to dispersion. Courtship occurs in two phases. During the aerial phase, the male pursues and often forces the female to the ground. During the ground phase, the butterflies copulate and remain attached for about 30 to 60 minutes. Only 30% of mating attempts end in copulation, suggesting that females may be able to avoid mating, though some have more success than others.
Adult Food Sources
Although larvae eat only milkweed, adult monarchs feed on the nectar of many of the following plants: Indian hemp, milkweed, aster, thistle, wild carrot, teasel, coneflower, horseweed, spotted joe-pye weed, common boneset, dame's rocket, alfalfa, goldenrod, lilac, red clover and tall ironweed. Monarchs obtain moisture and minerals from damp soil and wet gravel, a behavior known as mud-puddling.
Defense Against Predators
In both caterpillar and butterfly form, Monarchs are aposematic, warding off predators with a bright display of contrasting colors to warn potential predators of their undesirable taste and poisonous characteristics. Large larvae are able to avoid wasps by dropping from the plant or by jerking their bodies. Monarchs are foul-tasting and poisonous due to the presence of a substance in their bodies, which the caterpillars ingest as they feed on milkweed.
Additional studies have shown that different species of milkweed have differing effects on growth, severity and transmission of parasites.
After the caterpillar becomes a butterfly, the toxin shifts to different parts of the body. Since many birds attack the wings of the butterfly, having three times the toxins in the wings, leaves predators with a very foul taste and may prevent them from ever ingesting the body of the butterfly. In order to combat predators that remove the wings only to ingest the abdomen, Monarchs keep the most potent part in their stomachs.
Bird predators include brown thrashers, grackles, robins, cardinals, sparrows, scrub jays, pinyon jays, black-headed grosbeak, and orioles.
Parasites are also a problem with the survival of Monarchs. Infection from certain parasites create an effect known as culling whereby migrating Monarchs that are infected are less likely to complete the migration. This results in overwintering populations with lower parasite loads. Parasites can be controlled more easily in commercial breeding operations.
Human Interaction
The Monarch is the state insect of Alabama, Idaho, Illinois, Minnesota, Texas, Vermont, and West Virginia. It was nominated in 1990 as the national insect of the United States, but the legislation did not pass.
Monarchs can be attracted by cultivating a butterfly garden with specific milkweed species and nectar plants. Efforts are underway to establish these Monarch Waystations. Monarchs are raised as a hobby and for educational purposes.
Sanctuaries and reserves have been created at overwintering locations in Mexico and California to limit habitat destruction. These sites can generate significant tourism revenue.
Organizations and individuals participate in tagging programs. Tagging information is used to study migration patterns.
Monarchs are bred and used in schools, nature centers, hospices and weddings. Memorial services for 9/11 included the release of captive bred monarchs.
Habitat
Overwintering populations of Monarchs are found in Mexico, California, along the gulf coast, year-round in Florida and in Arizona where the habitat provides the specific conditions necessary for their survival. The overwintering habitat typically provides access to streams, plenty of sunlight (for body temperatures that allow flight), appropriate vegetation on which to roost and is relatively free of predators. Overwintering, roosting butterflies have been seen on sumacs, locusts, basswood, oak, osage orange, mulberry, pecan, willow, cottonwood, and mesquite. The Oyamel tree is the most common in Mexico for Monarchs. While breeding, its habitat can be found in agricultural fields, pasture land, prairie remnants, urban and suburban residential areas, gardens, trees and roadsides, anywhere there is access to milkweed. Habitat restoration is a primary goal in Monarch conservation efforts, habitat requirements change during migration. During the fall migration, butterflies must have access to nectar-producing plants. During the spring migration, butterflies must have access to larval food plants and nectar plants.
Migration
The eastern population migrates both north and south on an annual basis. The population east of the Rocky Mountains migrates to the sanctuaries of the Mariposa Monarca Biosphere Reserve in Mexico. The western population overwinters in various coastal sites in central and southern California. The overwintered population of those east of the Rockies may reach as far north as Texas and Oklahoma during the spring migration. The second, third and fourth generations return to their northern locations in the United States and Canada in the spring. Commercially bred Monarchs migrate to overwintering sites in Mexico adding to already existing data of migratory behavior. Not all Monarchs in the eastern population migrate to Mexico.
Habitat Loss Due To Herbicide Use
Conservationists attribute the disappearance of milkweed species to agricultural practices in the Midwest, where genetically modified seeds are bred to resist herbicides that eliminate milkweed nearby. Growers eliminate milkweed that previously grew between the rows of food crops. Corn and soybeans are resistant to the effect of the herbicide glyphosate. The increased use of these crop strains is correlated with the decline in Monarch populations between 1999 and 2010. Chip Taylor, director of Monarch Watch at the University of Kansas, said the "Midwest milkweed habitat is virtually gone" with 120 to 150 million acres lost. To help fight this problem, Monarch Watch encourages the planting of “Monarch Waystations.”
Loss Of Overwintering Habitat
The area of forest occupied in Mexico has been declining and reached its lowest level in two decades in 2013. However, the Mexican environmental authorities are now diligently monitoring illegal logging of the oyamel trees. The Oyamel is a major species of evergreen on which the overwintering butterflies spend a significant time during their winter diapause, or suspended development.
A 2014 study acknowledged that while “the protection of overwintering habitat has no doubt gone a long way towards conserving monarchs that breed throughout eastern North America,” their research indicates that habitat loss on breeding grounds in the United States is the main cause of both recent and projected population declines.
Climate
Climate variations during the fall and summer affect butterfly reproduction. Rainfall, and freezing temperatures affect milkweed growth. Omar Vidal, director general of WWF-Mexico, said "The monarch’s lifecycle depends on the climatic conditions in the places where they breed. Eggs, larvae and pupae develop more quickly in milder conditions. Temperatures above 95°F can be lethal for larvae, and eggs dry out in hot conditions, causing a drastic decrease in hatch rate."
Conservation
The Center for Biological Diversity, The Center for Food Safety, The Xerces Society and Lincoln Brower have filed a petition to the United States Department of the Interior to protect the monarch by having it declared an endangered species.
On June 20, 2014, President Barack Obama issued a Presidential Memorandum entitled "Creating a Federal Strategy to Promote the Health of Honey Bees and Other Pollinators". The Memorandum established a Pollinator Health Task Force, to be co-chaired by the Secretary of Agriculture and the Administrator of the Environmental Protection Agency, and stated:
In May 2015, the Pollinator Health Task Force issued a "National Strategy to Promote the Health of Honey Bees and Other Pollinators". The Strategy lays out current and planned federal actions to achieve three goals, two of which are:
Monarch Butterflies: Increase the Eastern population of the monarch butterfly to 225 million butterflies occupying an area of approximately 15 acres in the overwintering grounds in Mexico, through domestic and international actions, also public-private partnerships, by 2020.
Pollinator Habitat Acreage: Restore or enhance 7 million acres of land for pollinators over the next five years through Federal actions and public/private partnerships.
Many of the priority projects that the National Strategy identifies will focus on the I-35 corridor extending for 1,500 miles (2,400 km) from Texas to Minnesota that provides spring and summer breeding habitats in the monarch’s key migration corridor.
Conservationists are lobbying transportation departments and utilities to reduce their use of herbicides and specifically encourage milkweed to grow along roadways and power lines. Reducing roadside mowing and application of herbicides during the butterfly breeding season will encourage milkweed growth. Conservationists lobby agriculture companies to set aside areas that remain unsprayed to allow the butterflies to breed. Butterfly gardening will also increase the populations of butterflies.
Monarch Butterfly Garden
Remember Monarchs lay their eggs on milkweed plants and are the only food the Monarch caterpillars eat. Monarch numbers are declining, partly due to the loss of open spaces where milkweeds grow. You can help give monarchs a boost by creating a milkweed garden. Offer them food, drink, a place to stay and a milkweed patch where they can leave their eggs. Here is how to set up your own Monarch stopover.
Plant native flowering plants. Many butterflies and native flowering plants have co-evolved over time and depend on each other for reproduction and survival.
Include host plants. Butterflies lay their eggs on specific plants called hosts. Monarchs will lay their eggs on the leaves and the young caterpillars feed on the plant. The milkweed contains the toxins that the caterpillars must ingest, which causes the monarch butterflies and caterpillars to be poisonous to most predators. Milkweed flowers make a colorful splash in gardens, meadows, and other habitats. When flowering, they smell great. There are over 100 different milkweed species and monarchs use about 30 species. If you want to learn what native species are in your state, visit growmilkweedplants.com for a full list of native milkweed in your state or region, including Canada and Mexico.
If you can provide blooming flowers all summer long that will lure more butterflies, this would be a big plus because Monarchs need nectar from flowers all the time so choose plants that bloom in early, mid, and late summer.
Butterflies also need a place to rest. Flat stones offer them a place to bask in the sun and rest. Avoid insecticides because they kill insects. Include water. Butterflies can often be found drinking water and extracting minerals from damp areas of the ground. If you put coarse sand in a shallow pan and add it to your habitat butterflies will use it to drink and collect the minerals they need. Make sure to keep it moist by adding water.
Useful Sites And Publications On Monarchs And Milkweeds
The Xerces Society has launched a Milkweed Seed Finder database to make locating seeds in your state easier. Search for seeds in your state and contact the native plant nurseries that are listed to order milkweed seeds or plugs, then get planting! We recommend calling ahead to check availability of milkweed plants at the nurseries of your choice, as inventory can vary through the course of a season and from year to year.
Visit Monarch Watch’s Milkweed Market or directory of milkweed vendors to find native milkweed seeds and plants available in your region. The Milkweed Market offers flats of milkweed plugs (plants) that were grown from seeds sent to Monarch Watch by volunteers from across the country. Order plants grown from the seeds that were collected in your region, and make sure to collect and send seeds from your area to Monarch Watch next year.
For those of you in the desert southwest, the Southwest Monarch Study has a resource on their website with desert southwest milkweed providers and also provides more detailed information on establishing Monarch Waystations in this region.
Visit Monarch Watch's milkweed profiles page for more information on each of the recommended species.
For habitat restoration projects, we recommend using plant materials originally sourced as close to the planting location as possible. See the USFS Celebrating Wildflowers website for more information.
Additional tips on butterfly gardening can be found at the North American Butterfly Association's website.
Other Useful Resources:
Monarch identification and monitoring training video series produced by the Monarch Larva Monitoring Project.
Pollinator Habitat Tips produced by Pheasants Forever/Quail Forever.
Frequently Asked Questions about milkweed, provided by the Xerces Society.
Some of the other good sites are: livemonarch.com and thebutterflysite.com.