Many Missourians probably have memories of sitting outside on hot, heavy summer nights watching lightning bugs.
But during the last few years, there have been reports of fewer of the insect, which is why many Missourians have shared their surprise and pleasure at seeming to see more this year.
Steve Buback, a natural history biologist with the Missouri Department of Conservation, said numbers do appear to be up.
“We tend to think that firefly populations go in cycles with rain,” Buback said. “So, the last two years being kind of droughty – it’s their larval forms that are probably most susceptible to drought. So, a nice, wet year like this allows those little larval fireflies to survive a lot better, and so, I think that helps their adult numbers.”
Still, he warned, this increase isn’t necessarily an indicator of long-term population growth or recovery, as numbers are still drastically down compared to 50 or 100 years ago.
Buback said there’s lots of possible reasons for the reduction in firefly numbers, such as habitat loss. He said fireflies are most successful in areas of moist soil with tall, unmowed grasses, and this has become less common as time has gone on.
According to the Nature Conservancy, Missouri used to have 15 million acres of grassland as recently as the mid-1900s. Now, less than 1% of the prairie remains.
“We really just eliminated so much habitat,” Buback said. “You look at all the places we've impacted heavily, and they've just lost a lot of space to live. So, I think undoubtedly, numbers are down.”
The usage of pesticides and herbicides is also a major concern for firefly population health because the non-target effects of the chemicals may harm the insect, and the chemicals kill the food sources firefly larvae rely on.
Emily Althoff, an urban entomologist with MU Extension and Lincoln University, said fireflies actually spend the vast majority of their lives – years in some cases – as predatory armored larvae living in the soil and feasting on traditional garden pests, such as snails, slugs and earthworms.
“This cycle can go on for one to two years, depending on how much nutrients they're getting, depending on the species, climatic factors, etc., and then they'll become pupa, sort of like our butterfly life cycle. We know that that's that very complete metamorphosis. They completely change, is how I like to say it,” Althoff said.
She said the best way to ensure that fireflies populations stay healthy is to focus on the needs of the larvae and not just the more charismatic, “flashy” adults.
Luckily, while firefly conservation is not as simple and straightforward as planting more milkweed for monarch butterflies, there are still lots of ways people can help.
Althoff suggested leaving leaves in yards for longer periods of time and not mowing grass as often or as short – basically, anything that can help maintain a moist environment near the roots of grasses.
She added that minimizing light pollution around one’s home can also help fireflies, as the artificial light can distract and confuse the insect – making it harder for them to successfully mate.
“So, if you're around the house at night, you don't need to have all those lights on, maybe you can just have a few on,” Althoff said. “It helps your electricity bill, probably, and then also our fireflies and other components of our environment.”
Buback also recommended gardeners and homeowners use fewer chemical agents, as fireflies pose little risk to plants and even provide some natural “biological control.”
“Firefly larvae are going to be a great tool for you,” Buback said. “All you have to do is not spray them out, and they'll be doing their thing trying to find a meal and take out a slug or two for you on the way.”
Buback said that, ultimately, our knowledge of fireflies is “pretty incomplete. There are more than 40 species that have been identified in Missouri, and we don’t know all of the things that benefit or harm each species.
Still he encourages people to interact with the bug.
The most common type of firefly Missourians see is the "Big Dipper" firefly whose males fly in a J-shaped pattern trying to attract a mate. Buback said the most time of day to see fireflies is about half an hour before sunset to about an hour after sunset.
Althoff said she agrees it’s important for Missourians to continue to interact with the insect – though temporarily.
“I think catch and release is just fine,” Althoff said. "[It] really instills this core memory and care into the next generation of human beings and potential scientists and potential next generation of entomologists or conservationists and even just the general public, to care.
She just reminded folks to be gentle with the bugs and release them where you found them, so future Missourians might see the same number of fireflies their ancestors did.
For the audio transcript, click here.
