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Officials: Up to a third of nation's firefly species threatened with extinction; none yet in Michigan

Fireflies over and along a state highway in June outside West Athens, N.Y.
Pete Mauney for NPR
Fireflies over and along a state highway in June outside West Athens, N.Y.

There are more than 100 species of fireflies in the United States and up to a third of those are currently threatened with extinction.

One that is most at risk is the Bethany Beach Firefly, which can be found in Delaware, Maryland and Virginia in wetlands by beach dunes.

Richard Joyce is an endangered species conservation biologist with the Xerces Society. He said species of fireflies that live in wetlands and coastal areas are currently found to be the ones most at risk of extinction.

“I would say parts of the country that seem to be sort of hotspots for fireflies that are rare to begin with and vulnerable to these threats from humans … tend to be like coastal species and others like wetland fireflies,” he said.

There are 24 species of fireflies in Michigan. Currently none are at the risk of extinction, however, residents have seen less fireflies over the years, and this can be due to several reasons, Joyce said.

The most common firefly in Michigan is the Big Dipper firefly. These thrive in urban areas that are more developed.

“This is the firefly that a lot of people see in their backyards,” Joyce said. “And you can even see in like urban parks that have a lot of light pollution. Some people describe that species as the sort of the coyote of the firefly world because it’s really adaptable (and) can actually do pretty well in urban places.”

However, when people use pesticides in their lawn or grub killer, Joyce said it’s a good recipe for not having fireflies, due to them spending one to two years as larvae.

“Fields can be a good place to see fireflies if they have earthworms and tall grasses and wildflowers and that sort of thing,” he said. “Some human impact is actually okay for a lot of species.

But once you have a lot of tilling and light pollution and spraying of broad-spectrum pesticides. It’s not surprising that you would see fewer.”

Fireflies are the most active May through August, but each month varies with different species activity. Adults typically live two to four weeks. Joyce said it is easy to miss the window for a particular species to be active because of this.

The light pollution impacts the species ability to communicate and reproduce, meanwhile, those two to four weeks of adulthood are detrimental to reproduction.

Joyce said there are currently no good datasets that could define the percent of declining populations of firefly species.

“What we know is (that there) are real threats to populations,” he said. “There are numerous places that used to have fireflies that don’t have fireflies, but we haven’t (really) quantified that fully.

We can make guesses based on the rate at which habitats have been lost. You know, it’s been going on for decades.”

Without fireflies there is a risk of less healthy soils, Joyce said.

“For soil to be healthy it needs to have like all different kinds of organisms and decomposers in it, including, you know, insects and other invertebrates.

"And fireflies are an important part of that food web both in the soil for certain types of fireflies and in the kind of the leaf litter the decomposing plant matter right above the soil.”

Snails are fireflies’ favorite foods. Joyce said there may be certain habitats that species of fireflies may be that are indirectly benefiting plants by controlling the snail populations.

“That’s a little bit of a guess on my part because it hasn’t been hasn’t been studied,” he said. “The larvae are still pretty mysterious. We know little about their lives.

But just like wolves would control a deer population, for example, and that has impacts on the vegetation. The fireflies, you know, could be controlling snails and slugs, which also have an impact in the ecosystem.”

Besides firefly species, Joyce said insects overall these past 10 years have been showing declines in both the number of insects and the diversity of insects in lots of different places.

Joyce recalled a quote by Aldo Leopold when thinking of the possibility of the impact of a world without fireflies.

“The first rule of tinkering is that you don’t know what you don’t know,” he said. “You don’t throw away pieces. Even if you don’t know what those pieces are doing.”

The Xerces Society and the Center for Biological Diversity submitted a petition in 2019 for the Bethany Beach firefly to be added to the endangered species list under the Endangered Species Act. Joyce said the service is still in the process of reviewing this assessment.

This year, the Xerces Society submitted new petitions to the U.S. Fish and Wildlife Service to make a decision about adding the threatened firefly species to the list. Additionally, the organization jumpstarted a project called Firefly Atlas to gather numerical data on how abundant certain species are to make conservation decisions.

There are several things that can be done to help prevent the further loss of species of fireflies, Joyce said. One way is by reducing or eliminating the use of insecticides or pesticides. When grooming one’s lawn, the firefly larvae and general grubs are baby beetles so they will be affected.

Joyce added that besides steering away from pesticides, if people tolerate more wilderness in their residential landscape such as allowing some leaves to remain once they fall or having more native plants, this cultivates a better habitat for fireflies.

“Another thing that will benefit the fireflies that come out when it’s truly dark is to really be thoughtful about outdoor lighting and only using outdoor lighting, where and when it is truly necessary,” he said.

This story was produced as part of the Michigan News Group Internship. Zipporah Abarca is working for WCMU this summer at The Alpena News.