• Sara Thompson

Monarchs Head South in Migration


Monarch butterflies clustered on a tree branch
Monarch butterflies cluster in Santa Cruiz, Ca, where they migrate to for the winter; Photo credit is Brocken Inaglory

By Sara Thompson

Special to the Enterprise


When thinking about migrating animals most people will think about birds. It is true that many bird species will migrate to spend winter closer to the warmer equator. Many insect species also migrate to avoid the cold, winter months. One of the most commonly followed is the monarch butterfly. Even though it is one of the most recognized insects, it has been declining and needs our help now more than ever.


Like all insects, monarch butterflies begin as eggs. The female monarch can lay, on average, 300-500 eggs, depending on the age and size of the female. Females will lay a single egg at a time and the process can take two to five weeks to complete. Once laid, an egg can take up to a week to develop before hatching. The larva, or caterpillar, will feed almost exclusively on the milkweed plants the eggs are laid on. Caterpillars will continue to feed and grow for several weeks, growing from a few millimeters at hatching up to nearly two inches in length. Once gown, the caterpillars search for a safe place to enter its pupa stage. They usually find a place under leaves or low hanging brush to form a chrysalis and there it will metamorphose into the adult monarch. Depending on temperature, the monarch will be in the chrysalis phase for one to two weeks. Once ready, the chrysalis will split open and the adult butterfly will emerge. It will hang, letting their wings fill with fluids, expand, and become strong enough for flight.


Monarchs only migrate when they are adults. The power of flight makes it possible for them to cover great distances. During summer, new adult monarchs will venture north. Although, caterpillars fed almost exclusively on milkweeds, adult monarchs will feed on nectar from a variety of plants and flowers and is a main pollinator in most agricultural areas. When the weather starts to get colder and the days shorter, monarchs will begin their migration south. Monarchs east of the Rocky Mountains migrate down to Mexico, Texas, and parts of Florida. West of the Rockies, monarchs will winter in parts of Southern California and the northernmost parts of Mexico. An adult monarch can fly up to 100 miles in a day, some travel a total of 3000 miles! California can expect to see monarchs migrating beginning in October, and they stay here wintering until warmer weather in March.


Even though monarch butterflies are one of the most recognized and popular butterfly species, their numbers are dwindling. Researchers in California have been counting migrating butterflies for decades, and each year there are fewer and fewer. Their drop in numbers is due to several factors including loss of habitats, pesticide use, climate change, and more. Planting milkweed is one way to help, as monarchs lay their eggs exclusively on these plants. Also planting butterfly attracting flowers will provide nourishment to migrating adults.


Come explore our exhibit Healthy Planet, Healthy You exhibit to learn about how pollinators contribute to the foods we eat and other ways we all can help contribute to the health of our planet. Visit during our Public Hours: Friday 1-4pm, Saturday and Sunday 10am-2pm. Make and take crafts available for children before noon on weekends, while supplies last.


 

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