We don’t have the data to say that fireflies are disappearing, but that doesn’t mean we shouldn’t worry

  • A man is silhouetted by his phone as he attempts to make a photograph of fireflies, as they twinkle in the darkness while feeding on a type of mangrove tree, at the Kampung Kuantan Firefly Park in Kuala Selangor, Malaysia, on Wednesday, Oct. 9, 2013. (AP Photo/Jacquelyn Martin) Jacquelyn Martin

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    "Silent Sparks" by Sarah Lewis Courtesy—Princeton University Press

Published: 7/25/2016 6:29:19 PM

It’s a funny thing that people love bugs with “fly” in their name, as long as they’re not actually flies.

We like butterflies but not houseflies, dragonflies but not horseflies.

And what about fireflies? Well, everybody loves fireflies, including somebody like me who was raised in Virginia, where summertime fields are full of the beautiful blinking bugs.

So it was with considerable dismay that reports surfaced earlier this summer saying firefly populations were crashing, similar to what has happened to honeybees. My wife and I had commented to each other that we haven’t seen many of them this year, so I got alarmed and hunted around for a local expert to reassure me.

I found Tufts University biology professor Sara Lewis relaxing in Holderness. Her lab studies fireflies, which are actually beetles, and she has just published an excellent book about them, titled Silent Sparks. (Her lab also studies flour beetles and perhaps if they were called “flourflies,” publishers would have been interested in them, too.)

Lewis told me not to worry. Actually, that’s not really true: She said there isn’t data to support my worry.

“We don’t have long-term numbers on firefly populations,” she said. “It’s tricky because like any insect, populations go up, they go down – they’re very sensitive to local environmental conditions. . . . In a wet spring there are more, a dry spring less.”

So we can’t say that firefly populations are crashing because we’ve never done a census. But we can say, Lewis added, that there’s plenty of reason to worry.

“I am an ecologist, so I’m concerned with things like habitat loss, light pollution – but I also don’t want to be alarmist about this,” she said.

The big concern, as you are probably not surprised to hear, is habitat loss. From mangrove swamps in Southeast Asia, which support the eye-popping displays of synchronized fireflies, being turned into shrimp farms to wetlands in the U.S., which are being developed, human activity is often incompatible with thriving populations of these illuminated beetles.

“We have a lot of anecdotal evidence that suggests in places where there used to be firefly populations there are now parking lots and shopping malls,” is how Lewis put it.

Light pollution is a bigger concern for fireflies than for most other wildlife because those flashes are designed to find mates. If the flashes are hidden by our backyard security lights, the result is like turning on security lights at Lovers Lane on a Friday night – no connections are made.

Talking with Lewis showed me that fireflies are even more interesting than I realized. For example, I learned there are 150 species of them but many are “dark fireflies” – fire-less fireflies, so to speak, which lack the weird internal chemistry that creates bioluminescence.

“They are cool,” said Lewis, speaking metaphorically rather than of temperature. “That’s the ancestral state – the original biology (of the flashes) was a warning signal to repel predators; and a whole bunch don’t light up at all.”

Even the lightning bug fireflies we know and love are much more complicated than I thought. They live as long as two years around here, but almost all of that time is spent in the egg-larval stage, burrowed in the soil. The flying beetles are merely the adult stage, which lives for just a few weeks amid a haze of lust and longing.

So they’re interesting as well as neat to look at, and should be preserved. So how do you and I help?

“One thing that everybody could do is create an inviting habitat in your own backyard. They live in moist conditions. Every stage of the firefly life cycle needs water; they don’t do well in dry conditions. . . . Leave the grass a little longer or leave some leaf litter – that’s great for larvae to develop,” Lewis said. (Unfortunately, this is also a way to increase tick populations in our yards.)

Lewis also recommends against using pesticides to kill lawn-damaging grubs in the soil. “Those are not specific; they’ll also kill firefly larvae,” she noted.

And in the summer, turn off outdoor lights if you ever see fireflies. Heck, turn them off anyway and enjoy the stars.

On a bigger scale, we can support local zoning laws and environmental regulations that preserve wet areas. This isn’t easy, especially when those wet areas are on your own property, but it can make a difference in many ways.

In the meantime, take a moment to head out at night in the darkest, dampest place you can find, and maybe you’ll see one of the most delightful scenes that nature provides. No, I’m not talking about the mosquitoes.

(David Brooks can be reached at 369-3313, dbrooks@cmonitor.com or on Twitter @GraniteGeek.)

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