As hikers emerged from the woods and sprawled out onto the dark, open field behind the Eastman Nature Center in Maple Grove, there were several long moments of palpable disappointment.
It was a little after 9 p.m. As they hiked through the woods, the sky had faded from dusk to dusk, leaving only a thin strip of light on the distant horizon. Hikers were confused. There they were at the climax of the journey, the part they had all been looking forward to, and the prairie grass, swaying in the deepening shadows, seemed lifeless.
Then, slowly, the field began to sparkle.
“They’re starting to come out!” someone shouted.
“There’s one right in front of you!” someone else said.
A point of light rose in the air here, another flashed there, then a few at a time, then a dozen more, their number gradually increasing until fireflies soared and swooped all around , as if the insects had been waiting for their guests to arrive. so they can get the party started.
And fireflies know how to party.
Charismatic insects are the focus of firefly hikes, held annually in Eastman since 2018, a summertime tradition that can provide treasured memories for those who experience it.
“I think the one word was magic,” said Pam Heilman of Bloomington. In addition to last month’s hike, she took a naturalist-guided hike several years ago in Hyland Lake Park Preserve in Bloomington, which, like Eastman, is part of the Three Rivers Park District. “I don’t think I’ve ever seen anything like this in the wild before.”
What happened to them?
Many people remember seeing lightning bolts as children and wonder why they’re not there anymore, said Eastman naturalist Miranda Jones, who started the evening with a presentation on fireflies. (Jones and two other experts talk about fireflies in episodes 54, 55, and 56 of a Three Rivers podcast called “The Wandering Naturalist,” and even more information can be found on this Three Rivers blog.)
If you grew up, say, in a developing suburb of Twin Cities where there were once lots of fireflies but aren’t there anymore, look around you and notice what else is missing. Did you, as a child, play in grassy fields or patches of forest? Are these areas still there or have they been replaced by streets and houses?
Pesticides and light pollution, which obscures their flashes, have also contributed to the decline in firefly numbers, Jones said. And from 1960 until the mid-1990s, the Sigma Chemical Co. harvested about 3 million wild fireflies each year for the chemicals that produce their light, paying collectors nationwide a penny per insect. This practice is now prohibited.
Fireflies are still at home in suburban areas, Jones said, as well as in clearings and the edges of streams. They like areas with water sources.
“They really like logs and moist ground,” Jones said.
Fireflies are beetles, whose soft bodies are protected by hard wing shells and flat shields above their heads. “They can actually stick their little heads out and look around,” she said.
There are 2,000 species of fireflies worldwide, 120 in the United States and 6 in Minnesota. They come in slightly different colors and flash their lights in different patterns. Their glow is used to attract mates and ward off predators.
Some are oxymoronally called “dark fireflies” – they attract mates using pheromones rather than lights. Others, in addition to multisyllabic scientific names, have fanciful nicknames such as “Black-Bordered Elf”, “Woodland Lucy”, and “Big Dipper”. There are femme fatales who attract males of other species… and devour them.
“Their lives are incredibly complex,” Jones said, describing the stages.
The lifespan of fireflies begins with a few weeks as eggs, so small – “Dippin’ Dot size”, she said – their glow cannot be detected with the naked eye.
Then, up to two years, they are larvae. “Very, very strange and mysterious creatures, almost like a cross between a centipede and an armadillo,” Jones said. The lights on their backs repel predators. For most species, this is the only stage where they eat heavily, feasting on their favorite foods – snails, earthworms and nectar – after injecting them with the toxin.
They spend a few weeks in pupa, or pupa, form as their bodies transform, then emerge as adults who focus on finding mates. Male fireflies “fly away,” Jones said, while “the female, if she finds someone attractive, sends a signal.” When a man sees the signal, he approaches her and, well, they get intimate.
Then, following the typical ruthless pattern of insect life cycles, they die. The males leave immediately. The females lay the eggs of the pair first.
After this initial bewilderment, the hike was a success. Participants had been given nets and jars to – temporarily – capture lightning bugs so they could be examined closely. There were enough bugs around that anyone trying hard enough would succeed.
Aria Warner, 8, of Falcon Heights, managed to catch seven fireflies (she caught an eighth with her hands in the grass, but gave it to a girl who spotted it first). She briefly considered keeping them as a lamp.
But before leaving the field, the participants opened their jars and freed their glittering captives. And the fireflies resumed their cruise through the great grassy wilderness center, each hoping to find a mate and experience a few delightful moments before their earthly journey was over.
Firefly rides will return next June to Eastman, Three Rivers spokesman Tom Knisely said. Also coming this year, among many other outdoor activities, a dragonfly festival will be held on July 16 in Eastman. All Three Rivers Nature Centers will host butterfly programs in late August and early September as monarchs begin their annual migration to Mexico.