Danaus plexippus
Iconic migratory butterfly known for its orange-and-black wing pattern and extraordinary long-distance migration to Mexico. Listed as Endangered in Canada.
Seasonal Activity
Diet
Nectar (adult); Milkweed foliage (larva)
Lifecycle
Multigenerational migration. Overwintering adults in Mexico migrate north in spring, laying eggs on milkweed in the southern US. Subsequent generations continue north, reaching Ontario by May-June. Summer generations breed in Ontario. The final generation (late August-September) migrates 4,000+ km to overwintering sites in central Mexico.
Ecology
Host Plants
Native Habitats
Details
Description
The Monarch is one of the most recognized butterflies in the world, known for its orange-and-black wings with white spots and its extraordinary long-distance migration. Wingspan ranges from 9-10 cm. Listed as Endangered under the federal Species at Risk Act (SARA) and assessed as Endangered by COSEWIC in 2016.
Lifecycle
Monarchs undergo complete metamorphosis: egg (3-5 days), larva (10-14 days, 5 instars), pupa/chrysalis (10-14 days), and adult (2-5 weeks for summer generations; up to 8 months for the overwintering generation).
The migratory generation emerges in late August and September in Ontario and undertakes a 4,000+ km journey to oyamel fir forests in central Mexico. This generation enters reproductive diapause and does not mate until spring. The northward migration is completed over 2-4 subsequent generations.
Ecology
Obligate host plant relationship with Asclepias species (milkweeds). Monarch caterpillars feed exclusively on milkweed, which provides them with cardiac glycosides that make both larvae and adults toxic to most vertebrate predators.
Adults nectar on a wide range of flowering plants, with preference for Asteraceae (asters, goldenrods, coneflowers) and Asclepias species. Critical nectar plants for fall migration in Ontario include Symphyotrichum (native asters) and Solidago (goldenrods).
Host Plants
All Asclepias species native to Ontario serve as larval hosts. Key species:
- Common Milkweed (Asclepias syriaca) - most widespread host
- Butterfly Weed (Asclepias tuberosa) - dry sites
- Swamp Milkweed (Asclepias incarnata) - moist/wet sites
Habitat
Breeds in open habitats with milkweed: meadows, prairies, roadsides, old fields, and gardens. Migrating adults can be found in any open habitat with nectar sources. Critical fall migration corridors include the Lake Erie and Lake Ontario shorelines.