the monarch butterfly
danaus plexippus
The Monarch butterfly is one of the world’s most well-known and recognized butterfly species. This large and beautiful butterfly is known for its seasonal migration. The Milkweed plant is the only plant on which the Monarch butterfly lays eggs and the caterpillars feed.
Host Plant(s) for Monarch Caterpillars
Milkweed (Asclepias spp.) There are over 100 species of milkweed in North America.
* spp. stands for several species
Diet/Nectar Plant(s) for the Monarch Butterfly
Monarchs will nectar on whatever is plentiful and flowering, including their host plant. They need a succession of nectar-bearing plants into the fall. Native flowers provide the best nutrition for butterflies; some of these are:
milkweeds (Asclepias spp.), Purple Coneflower (Echinacea purpurea), Black-eyed Susan (Rudbeckia hirta), Joe-Pye Weed (Eupatorium), Ironweed (Vernonia noveboracensis), Beebalm (Monarda didyma). Asters and goldenrods (Solidago spp.) are an important source of nectar in late summer and fall before their migration south.
The Monarch Butterfly
The Monarch butterfly is a large, orange butterfly with black wing veins and black borders with white spots. Males have a dark spot along the vein on the hind wing. This dark spot is also a scent patch. The black vein lines on the female are thicker than on the male, and the female is slightly smaller.
Wingspan: 7.6 to 10 cm (3 – 4 in)
The bright colour of the Monarch is an indicator to predators that it may be unpleasant and toxic to eat. Monarchs acquire their toxicity from the Milkweed plant they consume in the larval (caterpillar) stage.
The Monarch Butterfly Range
Monarch butterflies range in North and South America, from southern Canada, the Maritimes (excluding Labrador), and south to Argentina. The wintering population is in Florida, Texas, California, and Central Mexico.
Habitat: Monarch habitat is anywhere that milkweed grows; often open meadows, fields, woodland edges, and wetland edges. During migration, they follow ridgelines, rivers, and coastlines.
Broods/Flight: The Monarch can have 4-5 broods per year. The summer generations fly from June through September.
Monarch Migration
The adults of the last summer or early fall generation go into a reproductive diapause and fly to their overwintering destination.
Eastern Monarchs fly south from my province of Nova Scotia, up to 4330 km or 2,690 miles. These adults can live up to nine months.
After overwintering, this generation flies north into the southern US, laying eggs along the way. They migrate northward in stages.
The Monarch butterfly is the only true, two-way migratory butterfly.
The Monarch Butterfly Egg
Monarch females can lay 300-500 eggs over 2-5 weeks. She lays the white, dome-shaped eggs singly on the milkweed leaf underside. They are the size of a pinhead and take about 4 days to hatch.
The Monarch Caterpillar
The caterpillars have wide black, yellow, and white bands. They eat the leaves, stems, and milkweed buds and acquire some toxicity from the host plant that helps protect the Monarch caterpillars and adult butterflies from predators. They shed their skin or moult as they grow. Intervals between moulting are called instars. They go through 5 instars. 5th instars may travel as far as 15 meters (50 feet) from the milkweed to find a sheltered place to form their pupa.
The Monarch Chrysalis or Pupa
The Chrysalis is a pale, waxy green with a horizontal string of gold dots near the top (not very visible in this photo). Monarchs spend 3-5 days in the chrysalis state.
Threats to the Monarch Butterfly
The Monarch butterfly is familiar but not considered common because their numbers have dropped by eighty percent in the past twenty years. They were designated as endangered by the International Union for the Conservation of Nature’s Red List of Threatened Species on July 21, 2022.
The most significant threats to Monarchs are:
- Habitat loss for the eastern Monarchs in the overwintering sites in Mexico, primarily due to illegal logging.
- Habitat loss for the western Monarchs in California overwintering sites due to encroaching development and aging trees.
- Breeding and nectar habitat loss in the USA and Canada has occurred because milkweed biomass has been lost due to housing developments, agriculture, and industry.
- Insecticide and herbicide use.
- Climate change, causing more severe storms and droughts.
What Can We Do to Help the Monarch Butterfly?
To help the Monarch butterfly you can create a Monarch butterfly garden by planting their host and nectar plants. To create a monarch garden, you must not use pesticides or herbicides on or near your garden. Milkweed is the host plant for the Monarch caterpillars; they cannot survive on any other plant. You will need at least 6 milkweed plants for the caterpillars to feed on. Caterpillars sometimes eat all the leaves off the plants, but Milkweeds are hardy and quickly regrow their leaves. Research what species of Milkweed is native to your ecoregion. Swamp Milkweed (Asclepias incarnata) is native to my Nova Scotian ecoregion.
You can find native plant guides for your ecoregion for both the USA and Canada HERE at ‘Pollinator Partnership’
An ecoregion map for Milkweed in the USA can be found HERE at ‘Monarch Watch’.
Swamp Milkweed needs:
• Light: full sun
• Moisture: moist to med
• Soil types: loam, clay, silt
• Height: 3-5 feet
• Bloom time: July-August
• Bloom Duration: 4 weeks
• Bloom colour: pink
You will need other, preferably native, nectar plants for the butterflies. Several shelter plants are also good for your butterfly garden for the caterpillars to form their pupae and for butterflies to retreat to in bad weather. Thornless shrubs and native grasses make good shelter plants.
Attracting Other Butterflies to Your Monarch Garden
Many other species of butterflies share the same nectar plants as the Monarch butterfly. By adding their particular host plants, you can attract them to your garden. Some of these butterflies profiled on this blog are:
Look but do not touch – please do not buy butterfly kits or chrysalis from commercial breeders or home-reared butterflies. This is cruel to butterflies, can create unfit populations and spread diseases to the wild species.
https://www.monarchscience.org/single-post/a-handy-summary-of-all-research-on-captive-reared-monarchs
Links to find out more about plants native to your area:
https://cwf-fcf.org/en/resources/encyclopedias/native-plant-encyclopedia
https://www.wildflower.org
Start building butterfly gardens:
https://davidsuzuki.org/take-action/act-locally/butterflyway
https://homegrownnationalpark.org
*Please subscribe to this blog for more posts on butterflies and native gardening.