Pollinators
Monarch Butterfly
Danaus plexippus
A butterfly whose entire eastern population funnels through Texas twice a year on a multi-generation journey between Canada and central Mexico.
Illustrated Species Ambassador
Aster — Monarch Butterfly
I'm Aster, an illustrated ambassador for the monarch butterfly. The journey between Canada and central Mexico takes more than one monarch lifetime to finish.
- One fact worth knowing
- The entire eastern monarch population funnels through Texas twice a year, travelling between Canada and a small area of oyamel fir forest in central Mexico.
- What I depend on
- I depend on milkweed across the whole breeding range for my caterpillars, on nectar corridors through Texas and the Great Plains in autumn, and on intact oyamel fir forest at particular elevations in Mexico.
- My greatest threat
- My greatest threat is the loss of milkweed and of overwintering forest.
- One way you can help
- Plant milkweed native to your own region — not tropical milkweed, especially in the southern states — add late-season goldenrod, asters and frostweed for the autumn migration, and stop using systemic insecticides in your yard.
This ambassador is an original illustration created for this project. It is an educational character, not a documentary image, and its statements follow the sourced record on this page. Artwork and rights record
Why this species matters
The monarch is the most recognized insect in North America and the easiest entry point into conservation for households. Because its needs are so specific — one plant genus for larvae, a nectar corridor in autumn, a particular forest in Mexico — it also teaches that habitat means specific plants in specific places, not just green space.
If it disappears: Losing the migration would end one of the best-documented long-distance insect movements on earth and remove a pollinator that also serves as the public's introduction to insect conservation.
Cultural and regional note: Monarchs arrive in central Mexico around Día de los Muertos, and their arrival is woven into the traditions of the region. Local communities are central partners in reserve protection.
Conservation status
- IUCN Red List
- Vulnerable (Danaus plexippus plexippus, migratory population)The migratory subspecies was assessed as Endangered in 2022 and reassessed to Vulnerable in 2023 following methodology revision.Last verified 2026-09-08
- U.S. Endangered Species Act
- Proposed for listing as ThreatenedUSFWS found listing warranted but precluded in 2020, and published a proposed rule to list the monarch as threatened with a 4(d) rule in December 2024. Confirm the current rulemaking status before publication.Last verified 2026-09-08
- Mexico
- Monarch Butterfly Biosphere Reserve, a UNESCO World Heritage SiteLast verified 2026-09-08
Population
The eastern population is measured as the area of forest occupied by overwintering clusters in Mexico, typically reported in hectares and generally well below the long-term average of recent decades. The western population is counted directly at California overwintering sites and has ranged from fewer than 2,000 butterflies in 2020 to tens of thousands in recovery years.
Trend: Decreasing
As reported: WWF-Mexico and CONANP annual overwintering area surveys; Xerces Society Western Monarch Count, most recent seasons
Source: WWF-Mexico / CONANP; Xerces Society Western Monarch Count
Uncertainty: Monarchs are never counted as individuals in the east. Reporting occupied forest area as a population number is a common error; keep the units accurate.
Historical: Eastern overwintering area was several times larger in the mid-1990s than in recent years.
Fragmentation: Two largely separate migratory populations, east and west of the Rocky Mountains, plus non-migratory populations elsewhere.
Range and distribution
Historic range: Across North America wherever milkweed grew, with overwintering in central Mexico and coastal California.
Current range: Same broad range, with much reduced breeding habitat across the agricultural Midwest.
Migration: A single southbound generation flies up to 3,000 miles to Mexico, overwinters, then the return north takes three to four successive generations. No individual completes the round trip.
Range contraction: Breeding habitat lost across the corn and soybean belt where milkweed once grew between rows.
Regions occupied
- Canada and the northern United States (summer breeding)
- Texas and the central flyway (migration)
- Michoacán and México State, Mexico (eastern wintering)
- Coastal California (western wintering)
Habitat
Primary habitat: Open habitat with milkweed for larvae and diverse nectar plants for adults — prairie, roadside, pasture, garden, and vacant lot.
Breeding habitat: Eggs are laid only on milkweed (Asclepias species); caterpillars eat nothing else.
Feeding habitat: Adults nectar on a wide range of flowers, needing late-blooming species for the southbound migration.
Seasonal differences: Overwinters in dense clusters in oyamel fir forest in Mexico and in eucalyptus, cypress, and pine groves on the California coast.
Habitat dependencies
- Milkweed across the entire breeding range
- Continuous nectar corridors through Texas and the Great Plains in autumn
- Intact oyamel fir forest at specific elevations in Mexico
Biology and ecology
A widespread pollinator and a major prey item for birds and invertebrates in some life stages.
Key relationships: Obligate relationship with milkweed; the toxins the caterpillar absorbs make the adult unpalatable to many predators.
Important adaptations: The migratory generation enters reproductive diapause, allowing it to live many times longer than summer monarchs.
- Size
- Wingspan about 3.5 to 4 inches.
- Weight
- Under half a gram.
- Lifespan
- Summer generations live two to six weeks; the migratory generation lives up to eight or nine months.
- Diet
- Milkweed as larvae; flower nectar as adults.
- Reproduction
- Females lay eggs singly on milkweed leaves.
- Offspring
- Several hundred eggs per female, with very high natural mortality before adulthood.
- Breeding frequency
- Multiple generations per year.
- Age at maturity
- About a month from egg to adult.
Primary threats
Loss of host plants
Herbicide-tolerant crop systems eliminated milkweed from millions of acres of Midwest cropland where it once grew between rows.
Overwintering habitat loss
Illegal logging and forest degradation in the oyamel fir reserves, and loss of California grove trees to development and age.
Pesticides
Neonicotinoid and broad-spectrum insecticide exposure kills larvae and reduces adult survival.
Climate change
Extreme storms at overwintering sites, drought along migration corridors, and shifting bloom timing all reduce survival.
Mowing during bloom
Roadside and pasture mowing during breeding season destroys eggs, larvae, and nectar supply.
Tropical milkweed and disease
Non-native tropical milkweed planted in the south does not die back in winter, encouraging monarchs to break migration and allowing the parasite Ophryocystis elektroscirrha to build up.
Habitat fragmentation
Gaps in the nectar corridor force butterflies to burn reserves they need for the wintering period.
Conservation and recovery
Programs and efforts
- Monarch Butterfly Biosphere Reserve protection and community forestry in Michoacán and México State
- Xerces Society Western Monarch Count and Western Monarch Call to Action
- Monarch Joint Venture habitat restoration across the central flyway
- Rights-of-way and roadside habitat agreements with transportation departments and utilities
- USFWS species status assessment and proposed threatened listing
Protected areas
- Monarch Butterfly Biosphere Reserve, Mexico
- California coastal overwintering groves under local protection
- Prairie preserves across the Midwest flyway
Legal protections
- Mexican federal reserve protection
- Proposed U.S. ESA threatened listing
- State and local overwintering grove ordinances in California
Measurable progress
- Illegal logging in the core reserve zones has been substantially reduced
- The western population rebounded from its 2020 low after coordinated habitat action
Continuing challenges
- Breeding habitat restoration must occur across millions of privately owned acres
- Climate extremes are increasing
- Public planting sometimes uses the wrong milkweed species
How people can help
What individuals can do
- Plant milkweed species native to your specific region, not tropical milkweed, especially in the southern states
- Plant late-season nectar flowers such as goldenrod, asters, and frostweed for the autumn migration
- Stop using broad-spectrum and systemic insecticides in your yard
- Delay and reduce mowing where milkweed and nectar plants grow
What communities can do
- Register schoolyards, churches, and parks as monarch waystations
- Ask city and county road departments to adopt reduced mowing schedules during bloom
Educational actions
- Participate in Journey North or the Western Monarch Count
- Raise monarchs only following state guidance, since mass rearing can spread disease
Habitat support
- Convert lawn to native prairie plantings
- Support corridor plantings along highways and utility rights-of-way
Organizations and programs to learn about
- Xerces Society
- Monarch Joint Venture
- Monarch Watch
- USFWS
Educational notes
- No individual monarch makes the round trip; the return north takes several generations.
- Occupied forest area in hectares, not a butterfly count, is how the eastern population is measured.
- Tropical milkweed is widely sold and is harmful in the southern United States — a good lesson in well-meant mistakes.
Sources and references
- IUCN Red List — Danaus plexippus plexippus — IUCN
- U.S. Fish and Wildlife Service — Monarch Butterfly — USFWS
- Xerces Society — Western Monarch Count — Xerces Society
- Monarch Joint Venture — Monarch Joint Venture