On the wing: Monarchs head south

Monarch butterfly/USFWS Midwest

Monarch butterfly/USFWS Midwest

On any given day in September or October, you may notice some large orange-and-black butterflies doggedly winging their way south. It’s the monarchs and what you are seeing is one leg in the most dramatic long-distance journey by any insect.

“For a long time their winter destination was a science mystery story,” explains Dick Walton, now director emeritus of New Jersey’s Monarch Monitoring Project (MMP). “In 1975 it was finally solved – the butterflies east of the Mississippi are headed to traditional wintering grounds in the mountain forests of central Mexico.”

A key tool in unraveling the secrets of monarch migration is tagging programs like the one run by the project in Cape May for more than 20 years. Small stickers fastened to the butterflies’ wings make it possible to track where those intercepted here eventually wind up.

Several generations of butterflies are involved in the annual fall trek from Canada and the United States to their winter retreats up to 3,000 miles away. Each spring, survivors make their way north again, beginning in late February. The first females to arrive in southeastern states lay eggs that produce young that continue on to northern breeding areas.

Scientists aren’t sure how migratory travel clues are passed from one generation to the next. Monarchs gather in sheltered Mexican forests to spend the winter, often in huge numbers. Early in the year, the simultaneous departure of millions of butterflies for points north is ranked as one of the great biological wonders of the world.

One spectacular fall day in October, I witnessed the curious gathered at Cape May State Park to see how the butterflies are tagged and sent on their way. Between Sept. 1 and Oct. 31, MMP volunteers who call themselves the “Monarchists” also take a daily census of butterflies passing New Jersey’s southern tip. Some are captured for tagging.

How do you transport a bundle of butterflies? Why, you carefully tuck them into small envelopes and pop them into a picnic cooler – the low temperatures ease the monarchs into a sleepy dormancy, warmth and solar power being the catalyst for butterfly flight.

After details of size and condition are recorded, a volunteer carefully scrapes off a patch of scales from the butterfly’s wing. (All butterfly wings are transparent, with tiny scales giving them their brilliant colors.) Once a small sticker is affixed, observers are invited to offer the monarchs a hand – literally – while they warm up and prepare for take-off.

“We’ve recovered some of our butterflies from their Mexican wintering spots, found one that traveled 140 miles in a straight line in a single day and retrieved one tagged here that three days later made it to central Georgia, 600 miles away,” Walton said reporting on results of years past. “Their migratory path goes down the coastal plain, along the gulf coast of Texas and then into the mountains of Mexico.”

Monarch populations fluctuate, but scientists are concerned about recent declines. Likely culprits are drought, high summer temperatures and the destruction of habitat, some of it turned over to vast fields of a single crop.

This makes monarch “waystations” – pockets of nectar sources for food and milkweeds for egg laying – important help for a threatened species. It’s one small way the average person can help keep these beautiful butterflies on the wing and in our skies.

Monarchs in hibernation./Felix’s Endless Journey/Flickr

Monarchs in hibernation./Felix’s Endless Journey/Flickr



Butterflies need nectar sources to fuel their life as winged adults. Among backyard plants that will do the job are asters, Black-eyed Susans, butterfly bush, cosmos, goldenrods, Joe Pye weed, purple coneflowers, sedums, verbenas and yarrows.

Monarchs uniquely need milkweeds – the only plant on which they will lay eggs and the only plant that caterpillars eat. By consuming the leaves they ingest the plant’s toxic compounds, making both larvae and adult butterflies unpalatable to predators. Three species native to New Jersey are: Asclepias incarnata, swamp milkweed; Asclepias syriaca, common milkweed; and Asclepias tuberosa, butterfly weed.

Milkweed sources:

Toadshade Wildflower Farm, 53 Everittstown Road, Frenchtown, NJ 08825. Call 908-996-7500 or visit toadshade.com.

D&R Greenway Land Trust, Johnson Education Center, One Preservation Place, Princeton NJ 08540. Call 609-924-4646 or see drgreenway.org. The trust operates a native plant nursery.

LiveMonarch.com will send you free milkweed seeds (although a small donation is welcome). See the web site or send a self-addressed, stamped envelope to: Live Monarch – Seed Campaign 2018, PO Box 1339, Blairsville, Georgia 30514.


Follow the latest on monarchs at MonarchWatch.org. Track sightings by citizen scientists as butterflies make their spring journey north from wintering grounds. Explore New Jersey’s own census and tagging project at MonarchMonitoringProject.com.


The Monarch Monitoring Program conducts public tagging demonstrations during the fall at Cape May Point State Park in cooperation with New Jersey Audubon’s Cape May Bird Observatory. Call the observatory at 609-861-0700 or see the online calendar.