Danaus plexippus

(Linnaeus, 1758)

Monarch, Monarch butterfly, Milkweed, Common tiger, Wanderer, Black veined brown

The is a large, migratory with distinctive orange, black, and white wing patterns. It is best known for its spectacular multigenerational between sites in central Mexico and coastal California and breeding grounds across North America. The has declined dramatically in recent decades, with the western declining 99.9% and the eastern population declining 84% since the 1990s. It was listed as Endangered by the IUCN in 2022, though it remains a candidate for listing under the U.S. Act. Conservation efforts focus on protecting milkweed plants and overwintering .

Danaus plexippus by (c) Jon Sullivan, some rights reserved (CC BY). Used under a CC-BY license.

Danaus plexippus by (c) Christine Young, some rights reserved (CC BY), uploaded by Christine Young. Used under a CC-BY license.

Monarch Butterfly Danaus plexippus Vertical Caterpillar 2000px by Photo (c)2007 Derek Ramsey (Ram-Man). Used under a GFDL 1.2 license.

Pronunciation

How to pronounce Danaus plexippus: //ˈdæ.nɔːs ˈplɛk.sɪ.pəs//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from the similar viceroy (Limenitis archippus) by larger size, lack of a black line crossing the hindwing, and different pattern. Viceroys have a single black line across the hindwing and are smaller. Queens (Danaus gilippus) are more brownish-orange with less distinct black veining and lack the bold white marginal spots. The black spot on the male monarch's hindwing is diagnostic for sex identification. No other North American butterfly combines the large size, bright orange color, and bold black-and-white wing pattern.

Images

Appearance

Large with wingspan of 8.9–10.2 cm. Wings display bright orange background color with thick black and borders, and white spots along the wing margins. Forewings are more pointed than hindwings. Males have a black spot on each hindwing containing androconial (scent scales), which females lack. The body is black with white spots. Underside of wings is paler orange with similar black veining. Caterpillars are banded with yellow, black, and white stripes and possess two pairs of black filaments (tentacles), one pair at each end of the body.

Habitat

Breeding consists of open fields, meadows, prairies, roadsides, and agricultural areas with milkweed plants. habitat in California consists of coastal groves of non-native eucalyptus, Monterey pine, and Monterey cypress that provide suitable microclimate conditions. In Mexico, overwintering occurs in oyamel fir forests at high elevations. Requires patches with 2–4 closely spaced milkweed ramets for successful larval development due to innate abandonment between ramets.

Distribution

Native to North America with two main migratory . The eastern population breeds across the United States and southern Canada east of the Rocky Mountains and overwinters in central Mexico (Michoacán and Mexico states). The western population breeds west of the Rocky Mountains and overwinters along the California coast from Mendocino County to San Diego County. Vagrant individuals occasionally reach Europe, Australia, New Zealand, and other regions. Australian populations are non-migratory and established.

Seasonality

In North America, are present during spring through fall with timing varying by latitude. The eastern undergoes a multigenerational : spring moves north from Mexico, summer generations breed across the breeding range, and the final autumn generation migrates south to sites. Western population adults migrate to coastal California overwintering sites in October–November and depart in February–March. Australian populations form non-breeding clusters during cool winter periods when maximum temperatures remain below 18°C for at least 2 days.

Diet

Larvae feed exclusively on milkweeds (Asclepias spp. and related in the Asclepiadoideae). Common milkweed (Asclepias syriaca) is a primary in the Midwest. Tropical milkweed (Asclepias curassavica) is frequently used in gardens but may disrupt migratory . feed on nectar from a wide variety of flowering plants including Mexican sunflower (Tithonia), bush (Buddleja), zinnias, blanketflower (Gaillardia), and other garden flowers.

Host Associations

Asclepias syriaca - primary larval plantCommon milkweed; primary in agricultural Midwest landscapes
Asclepias curassavica - larval plantTropical milkweed; frequently used in gardens but may disrupt if not managed
Asclepias fascicularis - native larval plantNarrowleaf milkweed; native to California but sometimes less preferred than tropical milkweed
Asclepias viridis - larval plantImportant for fall in southern U.S.
Asclepias physocarpa - larval plantCultivated in Central Mexico; use on crops reduces survival by up to 50%

Life Cycle

Complete with four stages: , larva (five instars), pupa (chrysalis), and . Females lay eggs singly on milkweed leaves, stems, or flowers. Eggs hatch in 3–5 days. Larvae feed on milkweed and sequester cardiac glycosides, making them toxic to most . Larval development takes 10–14 days under favorable conditions. occurs on milkweed plants or nearby structures; chrysalis is jade green with gold spots. Adults eclose in 9–15 days. Only 5% of eggs typically survive to adulthood under natural conditions. In the migratory , adults enter reproductive and do not breed until spring.

Behavior

Larvae exhibit innate milkweed abandonment , moving between ramets in random directions and requiring 2–4 non-natal ramets to complete development. have a perceptual range of approximately 50m and step length of 30m for movement modeling. Turn angle varies with milkweed . The autumn migratory undertakes long-distance directional to sites, with some individuals traveling over 600 miles. Non-migratory Australian form overwintering clusters during cool weather, with low temperatures (15°C) inducing reproductive dormancy and permitting long-distance flight, while high temperatures (19–28°C) inhibit flight and promote ovarian development.

Ecological Role

serve as for various flowering plants. Larvae sequester cardiac glycosides from milkweeds, becoming unpalatable and toxic to most vertebrate ; this chemical defense is retained in adults. Serves as alternative for the Trichogramma pretiosum, a natural enemy of lepidopteran pests. and larvae are preyed upon by spiders, ants, wasps, lady beetles, milkweed bugs, and even caterpillars.

Human Relevance

Iconic flagship for conservation and insect research. Declines have spurred extensive citizen science programs, restoration efforts, and policy discussions. Subject of extensive research in neurobiology of migration, chemical , and climate change impacts. Popular in gardens and educational programs. Tagged individuals are tracked through public reporting programs. Conservation concern has led to legislative funding for habitat restoration in California and petitions for federal protection in the United States.

Similar Taxa

Limenitis archippusViceroy ; similar orange and black pattern but smaller, with diagnostic black line across hindwing and different
Danaus gilippusQueen butterfly; similar but more brownish-orange with less distinct veining, overlapping range in southern U.S. and potentially competing for resources
Danaus chrysippusAfrican monarch/plains tiger; closely related Old World with similar coloration but different wing pattern details and non-migratory in most

More Details

Conservation Status

Listed as Endangered on the IUCN Red List in 2022. The U.S. Fish and Wildlife Service found listing warranted but precluded in 2020; the remains a candidate for listing with status review. Western declined from ~10 million in the 1980s to 1,914 butterflies in 2021 (99.9% decline). Eastern population declined 84% from 1996 to 2014. Primary threats include loss (165 million acres lost, including nearly one-third of summer breeding grounds), use (particularly glyphosate on herbicide- crops eliminating milkweed), climate change (drought, temperature extremes, severe weather), and logging at Mexican sites.

Movement Ecology Research

Radio telemetry studies using 393 tagged individuals determined that monarchs have a 50m perceptual range and 30m step length, with turn angles varying based on milkweed . Large steps influence landscape- movement patterns. These parameters inform agent-based models for conservation planning.

Tagging and Migration Tracking

Washington State University operates a tagging program for Pacific Northwest monarchs, primarily using inmates at Walla Walla Penitentiary for rearing. Tagged individuals have been recovered from San Mateo, California (330 miles in 10 days from Oregon) and Glen Ellen, California (600+ miles from Washington). Some Pacific Northwest monarchs may migrate to Mexico rather than California coastal sites.

Genomic Characteristics

The monarch contains 6.21% , substantially lower than close relatives Danaus chrysippus (33.97%) and Danaus melanippus (11.87%). TE content is three-fold higher around immune genes compared to other genes. Two novel Tc1 have expanded recently. LINE fragments show signatures of genomic deletions indicating high TE turnover rates.