Nature Notes: The Importance of Monarch Butterflies
By Anna Foster
The Monarch butterfly (Danaus plexippus) symbolizes summertime, appearing year after year in meadows, gardens, and front yards of houses. As of July 21st, this once abundant butterfly is now listed by the International Union for the Conservation of Nature as an endangered species. Populations across the United States have been in decline for some time. During the summer months, you’ll find a monarch enclosure in our Nature Center, where we rear monarch butterflies for educational and scientific purposes.
Monarch butterflies are easily recognized by their orange and black painted wings, spreading between 7 and 10 centimeters wide. In their larval form, the monarch caterpillar can be identified by its bright black, yellow, and white stripes. You’ll find monarch caterpillars on milkweed, their sole source of food, and the only location where monarchs lay their eggs.
The lifecycle of the Monarch begins with a female butterfly laying an egg on the underside of a milkweed leaf. The egg will hatch, and the caterpillar that emerges will begin to eat the milkweed on which it hatches. Monarch caterpillars will go through five instars, or stages, in their growth. Between each instar, they shed their skin to grow bigger and bigger. After 10-14 days, the caterpillar will hang in a “J” shape on the underside of a milkweed leaf or nearby structure, shedding a final time to create a chrysalis. Again, the Monarch will be in its chrysalis for 10-14 days, until the chrysalis becomes transparent, and the Monarch hatches as an adult butterfly.
There can be up to four generations of Monarch butterflies in one summer, and only the last generation migrates each year. For the first four generations, their purpose is to mate with other Monarch butterflies and lay eggs on milkweed plants. The last generation, which migrates south, does not breed.
Monarchs are a symbol for important pollinators in our ecosystem. Pollinators are responsible for ecosystem health, plant reproduction, and the pollination of many of the fruits and vegetables we eat! Come September, the last generation of Monarchs will begin their migration to Mexico, where they overwinter before returning north in the spring.
Monarchs are also an important cultural symbol in Mexico. Every year, thousands of monarchs migrate down to the mountains in the country’s center. Masses of butterflies arrive on November 1st and 2nd, at El Día de Los Muertos. This magical migratory phenomenon marks a symbol for the returning spirits of those who have passed away.
The three most significant threats to Monarch populations are deforestation in central Mexico, changes in weather patterns due to climate change, and loss of native plant habitat. However, parasites such as Ophryocystis elektroscirrha (OE) and the tachinid fly are also concerns. OE in particular has been increasing in occurrence in recent years. The parasite spreads through microscopic spores on adult butterflies. Once an infected adult lands on a milkweed plant or lays an egg, the spores spread to caterpillars. The parasite can cause deformity in hatched adult monarch butterflies and even cause death in the pupal stage.
OE is a huge issue for monarch populations in the western and southern United States, where monarch populations can survive all year, perpetually spreading the virus among milkweed plants. In places like Door County, OE is less prevalent because our monarchs and milkweed plants are seasonal.
At The Ridges, we have trained naturalists that can closely monitor the monarchs in our Nature Center enclosure. We are able to control parasites such as OE and tachinid flies. We do not recommend that individuals rear Monarchs on their own without proper training and care. However, there are many things you can do to help Monarch populations without rearing butterflies!
Planting native pollinator gardens creates essential habitat for pollinators, including Monarch butterflies. You can learn more about pollinator gardens in our last blog post (https://www.ridgessanctuary.org/nature-notes-pollination-and-conservation-in-a-fragile-sensitive-environment/). Planting native milkweed varieties will specifically benefit Monarch butterfly populations. In addition, joining efforts in your state to save grasslands, supporting wildlife corridors and pollinator projects, and protecting monarch habitat are other ways to help the Monarchs. Lastly, avoid using pesticides and insecticides in your garden or on your lawn. There are many natural ways to control pests, invasive plants, and weeds that won’t harm pollinators. You can learn more at www.pollinator.org.
Want to learn more about Monarchs? Join us for Monarch Madness on August 27th at our Nature Center. Learn about Monarch butterflies, their migration, and tag a Monarch butterfly for $5 before it makes its migration south to Mexico! For more information, visit our website at www.ridgessanctuary.org or call us at (920)-839-2802.