For anyone who’s noticed an abundance of monarch butterflies in recent days, the spectacle is no illusion.
The peak of this year’s monarch butterfly migration began the last week in August, but the butterflies some years will migrate to their wintering grounds in Mexico into late October, said Laura Bell, a naturalist at the University of Minnesota Crookston.
The metamorphosis from egg, to caterpillar, to chrysalis, to butterfly typically takes about a month, according to the Minnesota Department of Natural Resources.
As many as 50 million monarchs migrate south each fall to wintering grounds in the mountains and hills west of Mexico City, the DNR said.
Based on anecdotal reports, this has been a banner year for monarch butterflies, and many homeowners and nature watchers say they’ve been seeing huge numbers of monarchs in recent weeks.
When those butterflies head south depends on the hatch, Bell said Thursday, Aug. 29, while tagging monarchs in the Shaver Butterfly Garden on the UMC campus. Affixed to the butterflies’ lower right wing, each sticker has a unique identification number and a toll-free number to call and report a return.
Turtle River State Park west of Grand Forks also has been tagging monarch butterflies this summer, and only about 15 of the 85 or 90 have yet to hatch, park naturalist Erika Kolbow said Monday, Sept. 9.
“We’re kind of past the peak,” she said.
Tagging the butterflies is a popular attraction among park visitors, she said.
“Everybody loves them,” Kolbow said. “Whether it’s older folks going, ‘I used to see so many of these as a kid’ or ‘we used to raise them in school.’ It’s just that admiration of life.”
According to Monarch Watch, the conservation group that oversees the tagging program, monarch butterflies that emerge in late August and migrate south from North Dakota and Minnesota, are “biologically and behaviorally different” from those that hatch earlier in the summer.
These late butterflies won’t mate or lay eggs until next spring, saving their energy instead to migrate more than 2,000 miles to forests high in the mountains of Mexico to overwinter, Monarch Watch says. They’ll leave Mexico in late March, flying north and east to breed.
“It is these newly emerged monarchs, the offspring of the butterflies that made the fall journey, that recolonize their parents' original homes,” Monarch Watch says. “Summer monarchs live a much briefer life than the overwintering generation; their adult lifespan is only three to five weeks compared with eight or nine months for the overwintering adults.
“Over the summer, there are three or four generations of monarch butterflies, depending on the length of the growing season.”
Numbers increase throughout the summer until there are millions of monarchs heading south from the U.S. and southern Canada, yet another colorful sign of fall.
Other butterflies sometimes mistaken for monarchs
A butterfly sometimes mistaken for the monarch butterfly is the painted lady, or thistle butterfly.
Like monarch butterflies, painted ladies in North America migrate to Mexico. According to the website, “Butterflies and Moths of North America,” the painted lady is the most widely distributed butterfly in the world.
While the dorsal side of the painted lady butterfly’s wings is orange, black and white like a monarch, the hind side of the wings -- visible when closed -- is more of a brownish color and features two large “eye spots” near the back of the wings.
As a species, the painted lady is described as “demonstrably secure globally,” and no population concerns exist.
Erika Kolbow, naturalist at Turtle River State Park, said people tend to view the monarch butterfly as “more iconic.” The viceroy butterfly, which has similar markings, is most often confused with the monarch, she said, and people also sometimes mistake mourning cloak and red admiral butterflies for monarchs.
-- Brad Dokken