Rare butterfly spotted in Detroit park, ‘first in decades’

Regal fritillaries were once more common in Michigan. But with so much prairie habitat loss, it is considered a vulnerable species.
Regal fritillary atop wild bergamot. Photo courtesy of Leonard Weber.

Local naturalist Leonard Weber was standing in a field of wildflowers on July 4 last year, admiring the butterflies and other pollinators flitting and hovering about. 

Weber frequents this particular Detroit park often, spending a few hours here most days and documenting what he sees.

“This is my retirement activity,” Weber told Planet Detroit.

On this particular day, he noticed a butterfly he could not readily identify. He snapped a few photos with his cellphone camera and watched it for a few minutes until it floated away. It wasn’t until he went through his summer butterfly photos months later that he realized what he had come across. 

Weber suspected it was a type of fritillary – a group of butterflies with about 30 species in North America.

But even with his years of experience, the exact identification was not coming easily. He thumbed through field guides and searched online without success. Then he began looking at fritillaries whose ranges do not extend into Michigan.

He finally narrowed it down to the regal fritillary, which lives in tallgrass prairie ecosystems. According to the National Parks Service, these prairies have steeply declined for years, with only 4% remaining of the 170 million acres that once covered the continent.

Leonard Weber. Courtesy photo.

This is the exact habitat type that ecologists have been working to restore in Detroit parks, like the one where Weber saw the fritillary. Several city parks have tallgrass prairies that have been reseeded with native plants and wildflowers. There have even been a few prescribed burns, as fire is essential to maintaining prairies.

Weber sent his photos to Ronda Spink, who works with the Kalamazoo Nature Center as the coordinator for the Michigan Butterfly Network, a group of citizen scientists that monitor butterflies on public property.

“She confirmed it and passed it on from there, and it got verified by state authorities as a regal fritillary, the first one in decades found in Michigan,” says Weber. The last time the regal fritillary was observed in Wayne County was 1931, according to the Michigan Natural Features Inventory.

Regal fritillaries are fairly good-sized butterflies with a wingspan of up to four inches. They are dark orange and black with white spots on their wings. The males begin flying in June, and the females join shortly after.

This butterfly was once more common in Michigan, with its range reaching from Colorado to Maine. But with so much habitat loss, the regal fritillary is considered a vulnerable species. According to Weber, state authorities were considering placing it on Michigan’s extirpated species list, meaning it is extinct locally. 

The largest known regal fritillary population exists further to the west. Spink said the closest might be in Kankakee, Illinois, about 60 miles south of Chicago.

“There’s a huge tallgrass prairie there, and we saw quite a few regal fritillaries. In Michigan, they just haven’t been spotted,” she said.

Weber’s sighting provides some hope the regal fritillary may be rebounding, but not without some caveats.

“Is there a breeding population in this area, or was this a wandering individual? It was a male, so I think it may very well be a migrant or wind-blown. Of course, everyone is hoping to see the possibility of whether there is a breeding population here,” Weber says.

Unlike the monarch butterfly, which lays eggs on milkweed leaves so that larva can immediately begin eating upon hatching, the regal fritillary does not lay eggs directly on its host plant – which are violets.

“Regal fritillaries just kind of drop their eggs randomly in the woods or near the host plant,” Spink said.

The females lay eggs in the fall, and larvae must hibernate over the winter for seven months under leaf litter and then find a violet plant to feed on in the spring. Each female lays up to 2500 eggs, which scientists think is an adaptation to high larval mortality rates. They think many die from starvation or predation. A female monarch, in contrast, lays around 300-400 eggs in her lifetime.

Due to the butterfly’s rarity, entomologists from Michigan State University advised Weber and Spink to keep the exact location where Weber found the butterfly concealed..

“There’s some concern among the conservation authorities that somebody might try to capture it for collection or might be enthusiastic and trample the habitat,” Weber said.

The sighting has attracted attention from government agencies after being reported in the Michigan Entomological Society’s newsletter.

“We have the U.S. Fish and Wildlife Service and the Michigan Department of Natural Resources interested in knowing if there is a breeding population there,” Spink said.

Despite the secrecy, Weber thinks it is important for people to know this sighting occurred in Detroit. Weber said he is glad the city is amenable to not mowing over every inch of open fields and letting some park areas return to their natural state. 

“This is a Detroit story,” Weber said. “It speaks to the value of letting things flower.”


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