Late summer simply isn’t complete without the return of monarch butterflies to decorate fields rich in golden and purple hues. If you’re like me, however, you’ve probably noticed the drastic decline of monarch populations over the last two years.
While there are many factors that have contributed to the decline of the monarch, research points to habitat loss as one of the primary culprits. Monarchs are specialist insects, meaning they rely on a particular plant to complete their life cycle. Monarch butterflies can only lay their eggs on milkweed. As a migratory species, it’s vital that milkweed be available along the monarch’s entire migratory route for reproduction to be successful.
Life cycle of monarchs
You may know that eastern North American populations of monarchs migrate 2,500 miles to overwinter in the mountains of Mexico, but did you know that their migration back to the U.S. in the spring and summer takes place over four separate generations of butterflies?
In February or March each year, butterflies that overwintered in Mexico come out of hibernation to find a mate. The female butterflies then begin their journey northward and eastward to find a place to lay their eggs. In March or April, butterflies lay eggs on milkweed plants and after about four days, the egg will hatch to reveal the first of five larval instars, or stages. These larvae are what we commonly call caterpillars.
The caterpillar feeds and grows for about two weeks before pupating, then spends an additional 9-14 days as a chrysalis. When the chrysalis is fully developed, the monarch butterfly will emerge. Newly emerged butterflies will once again begin the reproductive process by finding a mate, migrating northward and eastward, and laying eggs. The second generation of monarchs will emerge in May or June and the third generation in July or August. Each new butterfly generation lasts only two to six weeks before reproducing and dying.
The fourth generation of monarch butterflies, however, is very different from the three previous. In early fall, the fourth generation of monarch butterflies emerges from their chrysalides and begins the long journey south to overwinter in Mexico. While it takes three generations of monarchs to migrate north, only one generation makes the treacherous journey south in the fall. The future of monarch populations relies on the ability of this fourth generation to safely make it to Mexico.
Monarch decline
There are many factors that have contributed to the decline of monarch butterflies. During the winter of 1996-97, there were over 20 hectares of overwintering sites occupied by monarch butterflies in Mexico. This past winter, that area reached an all-time low of just 0.67 hectare of overwintering habitat.
Nasty weather events in Mexico, including heavy rain and freezing temperatures, can cause dramatic declines in monarch populations. A bad weather event in 2002 resulted in 80 percent mortality and another event resulted in 50 percent mortality in 2010. Illegal logging and pest damage also cause decline in overwintering habitat.
One of the greatest concerns of monarch decline is loss of reproductive habitat here in the United States. Changes in land use, including suburban development and agriculture, have resulted in loss of milkweed stands that monarch butterflies depend on to reproduce. Monarch Watch, an organization that promotes the conservation of monarchs, estimates that the United States is losing 6,000 acres of potential monarch and pollinator habitat each day due to development.
Plant milkweed
As a homeowner, you may be wondering what you can do to lend the monarchs a helping hand. You can start by planting milkweed in your home garden. Even just a few plants will provide reproductive sites for monarchs. Also plant nectar plants for adult butterflies. Cosmos, joe-pye weed and boneset are a few good choices to keep monarchs returning to your yard.
If you feel particularly compelled to help the declining monarch populations, consider creating a monarch way station in a home, school, or church garden. These way stations provide all the necessary resources that monarch butterflies need to thrive. These sites are also great tools to educate our youth about the importance of conserving such an iconic species.
If you’re interested in learning more about how you can help monarch butterflies, join Ohio State University Extension for Monarch Mayhem later this month. Speakers Carrie Elvey from the Wilderness Center and Sharon Treaster from Ohio State University will present talks on the biology and life cycle of monarch butterflies and share how you can create a certified monarch way station at home.
The program will be held at Furnace Run Metro Park, 4955 Townsend Road, Richfield, from 6 to 8 p.m. Aug. 28. The cost is $10. To register, contact Danae Wolfe at the telephone number or email address that follows this column.
Danae Wolfe is the Ohio State University Summit County Extension Educator for Agriculture and Natural Resources. If you have gardening questions, she can be reached at 330-928-4769, ext. 17, or wolfe.540@osu.edu.