Monarch Butterfly
Danaus plexippus
The orange migrant that always finds its way
The monarch butterfly is North America’s most famous long-distance migrant, its orange-and-black warning coloration signaling to predators the milkweed toxins stored in its body. Each autumn, the final generation of adults flies thousands of kilometers alone to a Mexican overwintering site it has never visited before.
Key figures
- Wingspan
- About 9–10 cm, one of the largest migratory butterflies in North America
- Weight
- Adults weigh about 0.5 g, yet can fly continuously for thousands of kilometers
- Lifespan
- Summer-generation adults live only 2–6 weeks, while the migratory generation can survive 8–9 months
- Habitat
- Open grassland, fields, and areas with milkweed; overwinters in fir forests of central Mexico
- Diet
- Larvae feed only on milkweed leaves; adults visit flowers to drink nectar from many plant species
- Navigation
- Uses the sun’s angle and an internal clock to set direction, migrating up to about 4000 km
Life cycle
Egg → Larva (five instars) → Pupa (hanging chrysalis) → Adult
Ecological role
Adults are pollinators of many wildflowers. Larvae feed exclusively on milkweed and store its toxins in their bodies through to the adult stage, forming a chemical defense against birds and other predators.
Did you know
The generation that completes the migration has never been to Mexico before. It steers by the sun’s position and an internal clock, switching on cloudy days to a backup system sensing Earth’s magnetic field.
Range
North America (breeding range from southern Canada through the United States to Mexico), overwintering in fir forests of central Mexico and along the California coast; introduced populations occur in Oceania and the Iberian Peninsula
Status
The migratory population has declined significantly since the late 20th century; listed as Endangered by the IUCN in 2022
Anatomy
- Forewing — Orange wings with black veins form a warning pattern that tells bird predators of the bitter toxins hidden inside
- Hindwing — A black scent-marking spot on the inner surface is the key feature for telling males from females
- Feeding tube (proboscis) — A long, coilable mouthpart that uncurls to reach deep into flowers and draw up nectar
- Antennae — Club-shaped antennae with swollen tips help sense scent and regulate the internal clock used for navigation
- Compound eyes — Wide-angle compound eyes help it recognize landmarks and track the sun’s angle during migration
- Abdomen — Stores milkweed toxins accumulated during the larval stage, forming a chemical defense against predators
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