How to set the right mood for the fireflies in your yard

Photo by Tony Phan

Seeing fewer fireflies this year? If you are, there could be many reasons for it, only one of which is completely normal and natural.

Justin Smith, director of environmental health for the City of Kent, said that if there are fewer fireflies, the city’s mosquito spraying program is not the culprit. The city only sprayed once last year and hasn’t done so at all this year, he said.

Spraying is triggered when the city’s test traps turn up mosquitoes that carry West Nile virus, Smith explained. None have so far this year.

Smith suggested that residue from chemicals people spray and broadcast onto their lawns and crops could be to blame, or even climate change.

Christie Bahlai, an entomologist with Kent State’s Department of Biological Sciences, agreed that the city’s spraying program is unlikely to affect fireflies — which, it turns out, aren’t actually flies at all.

“They are beetles, more closely related to weevils and ladybugs than flies. They are as different as cats and whales, maybe even more different,” she said.

Adult fireflies — or lightning bugs, as they are commonly called — are most active at dusk, which this time of year translates to between 7 and 10 p.m., peaking at about 9 p.m.

“Once it’s fully dark, you don’t see them much,” Bahlai said.

It would be easy to blame a perceived decline in firefly populations to one cause, but Bahlai said it’s more likely “death by 1,000 paper cuts.” It could even be a natural cycle.

A 2016 study suggested that firefly populations peak every six years, she said. Researchers saw a peak three years ago, so a down cycle now is expected. Even so, the total population does seem to be in decline, she said.

The weather and temperature extremes that climate change creates could well be one culprit, she said.

“We can have really hot days that can be deadly to any species,” she said. “When we talk about climate change, we’re talking about averages, but it’s really the extremes that hurt the insects. When you have a freak heat wave that happens at the same time as a drought, that can really hurt the insects.”

There’s also sex. Specifically, beetle sex.

The common eastern firefly, also known as the big dipper firefly, is the most common species in North America and is named for its signature mating dance.

“The male will be flying, and they do a J-shaped swoop while they’re flying, and that’s how the females recognize them. The females remain on the grass, but they start blinking to signal they’re receptive to his dance,” Bahlai said. “They like the J.”

However, since male mating dances are heat sensitive, the males may be emerging earlier and getting out of sync with the females, who spend most of their adult lives resting in the ground vegetation, she said.

Bahlai said fireflies live about a year, spending most of the time as larvae. The larvae live in the soil and may actually benefit from fertilizers. After all, more plant growth means more food for the larvae.

“Larvae eat critters that live in the soil, so if you have a lawn-pest outbreak, you might actually be fostering fireflies,” she said.

When fertilizers are mixed with toxic weed killers, though, firefly populations surely decline.

Changes in land use may also impact fireflies, which prefer open fields that don’t get too much soil disturbance, Bahlai said. Even there, spray drift from pesticides, weed killers or anything else wouldn’t do them any good.

To promote fireflies, people can support efforts to protect undeveloped land, especially prairies. Locally, the Portage Park District, which has a tax levy on the November ballot, champions conservation of huge hunks of the county’s land.

Bahlai encourages people to use pesticides as little as possible, or at least to use chemicals specific to the targeted problem. Planting medium-height native vegetation helps bees and butterflies as well as fireflies, though gardeners might find themselves battling deer to get the plants established.

“Less lawn, more garden,” Bahlai said.

Finally, sex again. Not to personalize matters, but lightning bugs, like many people, prefer doing it in the dark.

People can do their part by reducing light pollution. Instead of a fully lit yard, put outdoor lights on timers or motion detectors.

“These guys need to be able to see each other,” she said.

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Wendy DiAlesandro is a former Record Publishing Co. reporter and contributing writer for The Portager.