Monarch
Latin Name: Danaus plexippus
Species: Terrestrial Invertebrate
Conservation Status: S4-5 - Secure
With its iconic orange and black markings, the monarch is one of the most recognized and researched butterfly species in North America. They have 2 sets of wings, which are about 3-4 inches across, and their wings are a deep orange with black veins and white spots along the edges. Males have two black spots in the center of their back wings which are scent glands that attract females. The monarch catepillar can be up to 2 inches long, and is yellow, black, and white striped.
Range & Habitat (map)
Monarchs are native to North and South America but have spread to other locations with milkweed and suitable temperatures, including some Caribbean islands, Australia, and New Zealand. In North America, there are two populations of monarchs called the eastern and the western populations, separated by the Rocky Mountains. The eastern population migrates from Canada to Mexico over successive generations each year, overwintering in central Mexico. The western population spends the winter along the southern California coast. Recent studies suggest there might also be a distinct population of monarchs that spend the full year in coastal South Carolina, depending on swamp habitat in spring, summer, and fall; and spending winters on our Sea Islands.
Diet
As caterpillars, monarchs feed exclusively on the leaves of milkweed plants, which is why they are such an important wildflower in North America. Milkweed contains toxins that are harmful to most insects and other animals, but monarch caterpillars are able to process this plant without harm. As adults, monarch butterflies consume nectar from a wider range of blooming native plants, including milkweed.
Life History
The life history of monarchs is interdependent with milkweeds. Monarchs begin their lifecycle as eggs, which are laid on the leaves and stems of milkweed plants and hatch after 2-5 days. The larval stage of a monarch where it is a hungry caterpillar eating milkweed leaves lasts about 2 weeks. It then pupates into a green chrysalis, where it goes through metamorphosis over 1-2 weeks, and emerges a butterfly. Adult butterflies typically live 2-5 weeks, but the generation that reaches its wintering habitat can slow down its systems to survive up to 9 months.
Significance
The interdependence of this one butterfly species with milkweed plants, and its annual journey of as far as 2,000 miles over several generations to the same wintering grounds is a fascinating example of the wonder of nature. Even more exciting is the possibility that one monarch population spends its whole year in coastal South Carolina, rather than making this journey. Though considered ‘secure’ in South Carolina, the rapid decline of monarch population nationally over the last 3 decades is a red flag for problems in the environment.
Threats & How You Can Help
The monarch population has declined by approximately 90% since the 1990s, mostly as a result of habitat loss and habitat fragmentation. They are also harmed by the widespread use of pesticides, which poison the caterpillar and adult butterflies. One way you can help monarchs is to plant native milkweed plants in your yard and garden, and eliminate the use of harmful pesticides.
Additional Resources
US Fish & Wildlife – https://www.fws.gov/species/monarch-danaus-plexippus
Unique group of monarch butterflies discovered in coastal South Carolina – https://www.dnr.sc.gov/news/2023/Jul/jul11-butterflies.php
Monarch Watch – https://monarchwatch.org/