The familiar fluttering twinkle that decorates the summer night is nostalgic for many. Most associate fireflies or lightning bugs with warm summer nights, running through soft grass and watching a glass jar glow with buzzing illumination. However, some people claim to be noticing fewer lightning bugs in their backyards.
Richard Joyce is an endangered species conservation biologist with The Xerces Society for Invertebrate Conservation and the coordinator of Firefly Atlas, a firefly research and conservation initiative. He said that while anecdotal data indicates a slight decline, it’s not a black and white picture. Anecdotal data is a type of generalized data that comes from individuals contacting the organization to share an observation, rather than scientific data.
“Believe it or not, people haven’t really been doing lightning bug counts systematically for decades, so we don’t really have good numbers to work off of,” Joyce said.
Conservation attention is sparse for fireflies, which makes it difficult to pinpoint exactly how rapidly they are declining, according to Xerces. The sheer number of firefly species, the environment and a lack of existing data are factors that make the decline of fireflies hard to determine.
“There’s one called the big dipper for example, that seems pretty adaptable to the way that we humans have changed their environment,” Joyce said. “So I don't think that firefly is going to disappear any time soon.”
However, Joyce explained that there are certain species of firefly that are threatened. Xerces did a conservation assessment for North American fireflies in 2020, and they found that somewhere between one in six and one in three firefly species in the United States are facing some level of extinction threat, according to Joyce.
He added that a majority of Missouri’s firefly species are in the International Union for Conservation of Nature’s Red List category of “least concern.” This category means those species may be declining in some places but can also be found in a large range of different habitats, according to Joyce. He noted that there are some places where we just won’t see fireflies anymore because the way we manage the habitat doesn’t support them. Climate change, light pollution, pesticides and habitat loss and degradation due to urbanization are the most common threats that fireflies face.
There are over 170 species in the United States, according to Joyce. Missouri Department of Conservation Entomologist Steve Buback said Missouri is home to about 40 of them. Buback said that while anecdotal data can give an idea of a potential decline, they don’t have the hard data to scientifically determine it. He says the first step towards learning more about fireflies is telling them apart.
“Fireflies are pretty tricky to put names on because physically, a lot of them look very similar. We really need the flash patterns in order to tell them apart,” he said. “When we have a specimen that was collected 100 years ago, we don’t have any information on its habitat or its flash patterns. And so just tying all those strings together to tell a story is the first step, and that’s kind of where we are right now.”
Buback added that while they can’t scientifically determine their decline, he does feel that they are in decline based on anecdotal data. But it's challenging to tell which species, or how rapidly, without scientific data.
Xerces conducted a study through a past project called Firefly Watch. The study looked at community science data that was collected, and one model they addressed was firefly abundance and climate. They found that firefly abundance was highest in a balanced environment of warmth and moisture, according to Joyce. “So as the climate warms, I think some places that were good for fireflies in the past may be less so, especially if they get less rainfall,” he said.
How can we help?
Fireflies are both harmless and a vital part of a healthy ecosystem. Buback said that while the adults are a smaller part of the ecosystem, the larvae that are found crawling around feed on harmful pests like slugs and snails, making them beneficial for gardens and maintaining the balance of a healthy environment. The larval stage of a firefly’s life is the longest, lasting around 8-10 months. This is the stage that they begin to feed on garden and lawn pests, so Buback said one of the biggest threats is having pesticides and other chemicals on your lawn that harm the larvae as they’re trying to feed. Similarly, fireflies are bioluminescent; a chemical reaction that causes those magical flashes of light. But, their flashing patterns are actually how they mate, and increasing light pollution can disrupt their mating process because they rely on the dark to flash.
Joyce said another way to help conserve fireflies is to make parts of our lawns firefly friendly.
“Have slightly taller grass and maybe let the leaves lie where they lie, because that’s all great firefly habitat,” he said.
Joyce added that contributing to science is an especially impactful way to conserve fireflies. He pointed to a group of naturalists in Bentonville, Arkansas.
“They go out and they try to document species they find,” said Joyce. “They take photos, they make notes about the flash patterns, and they’re really helping us to fill in the map of what species are found where and how they are doing.”
