Friday, August 19, 2022

Security Lights Threaten Faerie Lights

As a kid, many a June twilight was spent trailing the beacons of fireflies in the deepening dusk to try and catch them in my hands. I was endlessly enthralled. Endlessly until Mom called to clean up for bed, at least. It pleases me that my own two children went through this phase, presenting me with Mason jars of flashing green magic before they released “their” fireflies outdoors. For the longest time, I remained enchanted by those shimmering, summer-night faerie lights. These days I’m charmed only by the memory of such. They’re nearly gone from our farm now, a paltry few flashing in a meadow that once hosted a Milky Way of moving lights.


With 2,000 known species, fireflies are native to both the Americas and Eurasia. In the larval stage, they’re carnivorous, and eat many insects we consider pests. You may see young fireflies, grub-like “glowworms,” in the lawn or flower bed. Larvae also feed on worms, slugs and snails before wriggling down into the soil or other protected space to overwinter. After a short pupal stage, they emerge to mate. Adults mainly subsist on pollen and nectar, though a few don’t eat at all in their brief grown-up phase.


Among the reasons fireflies have been well-studied is that they produce the most efficient light in the world, with 100% of the energy in the chemical reaction used for illumination. When the enzyme luciferase hits luciferin in the presence of magnesium, oxygen, and ATP, it results in light devoid of any heat (that comes later when they find a mate). Flash patterns and colors vary from one species to another, and among the sexes. It is more common for females to stay put and send out their Morse code while the guys work up the nerve to approach a mate.


Occasionally, flashes among disparate sexes and species will synchronize temporarily, something for which there is no explanation as yet, other than to flummox biologists. I have to say it’s “pretty cool,” technically speaking. The most common color of light is yellow, although it can be green, or even red, depending on species. In certain light conditions, some shades of green can be perceived as blue. Although the orgy of glitzy flashes in late spring and early summer is mainly to signal for a hookup, there are other reasons fireflies light up their butts. Both larvae and adults contain a bitter toxin which is closely related to the stuff toads make. Just as nothing eats toads – or at least not twice – due to their toxicity, predators don’t knowingly eat fireflies.


It is believed that juvenile light-shows are to advertise that they’re unpleasant to eat, thus avoiding predation. Biologists call overt markers such as this and the bright colors of poisonous frogs “honest signals.” At least one type of cannibalistic firefly mimics the flash pattern of another species, luring those males in with the promise of sex only to eat them. I’m guessing this would be a “dishonest signal.” Fireflies’ light-emitting chemicals are used in medicine to detect blood clots, tuberculosis, diabetes, and some cancers. For most applications the chemicals are now synthesized, but a small percentage is still harvested from fireflies, a practice which must soon be halted.

Fireflies. Wikimedia Commons photo.

I highly recommend the superb and heartbreaking 1988 Anime film Grave of the Fireflies, which is based on a true story. For the younger of the two child-protagonists, fireflies bring joy. Her older brother, though, sees in fireflies the souls of the war-dead rising to heaven, as well as the daily barrage of firebombs which has left them homeless orphans. While not as poignant as children suffering the effects of war, the story of today’s fireflies is sad nonetheless. The eerily glowing beetles are at risk worldwide, and according to entomologists, many firefly species may soon be extinguished altogether.


A year-long Tuft University study, published in February 2000 in the journal BioScience, surveyed firefly populations in North America, Central America, Europe, South Asia, East Asia, and Southeast Asia. It found that in every region, fireflies are in trouble. But it’s not only fireflies. Insect populations are in freefall everywhere: Between 1996 and 2016, Ohio lost a third of its butterfly population. German scientists have documented a 75% drop in the number of flying insects in nature preserves in just the past 27 years. Not surprisingly, this has contributed to the loss of insect-eating songbirds. The causes of this alarming insect decline are complex, but pesticide use, climate change, and habitat loss are driving this die-off to a large extent.


Where fireflies are concerned, though, it turns out that exterior lighting is the second-most important factor in their decline, right after habitat loss. Most of us can’t individually make a dent in global warming, put a stop to urban sprawl, or curb the use of agricultural chemicals in the next 24 hours. But we can, literally, help fireflies overnight – by turning off exterior lights. Motion-triggered security lights can replace floodlights that run constantly. We can use lower wattage bulbs, and do away with outdoor lights which are used for aesthetic purposes only.


Being mindful of how we illuminate the outdoors is a small bother compared to losing fireflies. Perhaps if we can work to reduce light pollution in our communities, we’ll one day see thousands of shimmering
Tinkerbells on summer evenings again. Maybe our kids and grandkids will have the privilege of catching magic in Mason jars, and watching the procession of lights heavenward when they let the fireflies go.


For more information, see the report “A Global Perspective on Firefly Extinction Threats” at


Paul Hetzler, not the brightest bulb in the package, has dimmed his outdoor lights as well. He’s a former CCE educator. Thanks to Marie-Line Bourdy for suggesting this topic.


Photo at top: Firefly. Wikimedia Commons photo.


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Paul Hetzler has been an ISA Certified Arborist since 1996. His work has appeared in the medical journal The Lancet, as well as Highlights for Children Magazine.You can read more of his work at or by picking up a copy of his book Shady Characters: Plant Vampires, Caterpillar Soup, Leprechaun Trees and Other Hilarities of the Natural World


12 Responses

  1. Teresa Calafut says:

    I don’t understand why there is such a proliferation of outdoor lighting. I enjoy walking around the pasture at night, but now there are a lot of really bright floodlights. They are not close but still project a bright light. A neighbor once told me I should have outdoor lights. I asked him if he was afraid of the dark. I always like the fireflies – we always called them lightning bugs.

    • Boreas says:


      I understand WHY many modern humans fear the dark, and today as often as not, it is fear of other humans! So as usual, we try to alter Nature to assuage our fears. But we are just beginning to learn of the significant negative effects of unnatural lighting on Nature itself.

      Another thing that is helpful when choosing outdoor lighting is simply choosing well-designed shades that do not allow the light to go anywhere but down where it is “needed”. This simple change can dramatically affect light pollution in residential areas with street lighting.

      • Joe Kozlina says:

        I am 64 years old and have known how harmful these lights are to our enivornment since about 8 years old when a family member put up one of those lights to attract bugs and fry them with an electric store bought insect killing contraption. Anyone still use one of those? We still have a few night time insects still around. Can’t have that. Got to kill them all. The dusk to dawn era, the flood lights, the road lights, the solar side walk lights, the accent outdoor lighting. Look around, the whole earth is lite up for no particular reason except that we can. Fear, I FEAR the end of us, with all this waste. TURN OUT THE LIGHTS!

  2. SH says:

    I remember seeing lots of fireflies as a kid (along with the Milky Way) – both seemed to disappear until I moved out to a small lake in the woods and then both magically reappeared – until the lights from a new Mall nearby blitzed out the Milky Way again – I loved the fireflies …
    In the name of “progress” we seem to have stolen both the stars and the fireflies, and so much else, from our kids …

    Thank you for this post …

  3. Pat Boomhower says:

    NYS Conservationist magazine’s June 2018 issue had a great article about fireflies. It included a 2-page spread much like the photo here in Mr. Hetzler’s article. The DEC picture shows activity of the various species including the height & timing of each species. A wonderful tool for young & old to study before spending an evening watching faerie lights.

  4. Smitty says:

    Great article Paul. A nearby neighbor has 5 very bright flood lights on all night long that seem to serve no purpose other than to annoy. Maybe that’s why I see so few fireflies now.

  5. Charlie Stehlin says:

    “pesticide use, climate change, and habitat loss are driving this die-off to a large extent.”

    And what are we doing about it! It’s hard for me to read stories such as above, and I most certainly wont watch “Grave of the Fireflies” due to your ‘heartbreaking’ introduction to it. O’ the tortures that come with having a conscience!

    I live in a residential area in a concrete jungle where weeds outnumber flowers by a large margin, and ‘they’ (flowers) are threatened constantly by the city workers who mow every ‘thing’ in sight so as to maintain the cosmetic look; or are threatened due to my neighbors who are generally mindless which explains the trash everywhere… amidst the flowers, at curbside, along the walks, etc. Dog poop is more a common sight than butterflies are in my neighborhood, which does have its share of flowers but just not enough of them, and most always they are only small concentrated patches of them with trash nearby or at the ground below them where they took root.

    Everybody a certain age remembers lightning bugs. I recall a few years ago I saw a single lightning bug in my yard which was the most peculiar thing as I had never seen one prior nor have I seen one since, and I’ve been living here a dozen years. I still think about that one little bug with its light flicking on and off at night. I don’t know where the heck it could have come from as there is just nothing around here which would attract them. Strange!

    I got to talking with a woman whom I met recently, and she brought up lightning bugs; she said “when I was a kid there were lightning bugs everywhere, now I hardly see them at all!” She was saddened in talking about this. (A very common theme to those of us who remember Bazooka Joe bubblegum at a penny apiece.) Fireflies are still out there but not in the great numbers they once were, and then only in the areas which are rural, where there’s a lot of open space and fields and flowers where they don’t spray, or where they let the grass and flowers grow along the roadsides. That has been my experience anyway. Otsego County has fireflies in sizable numbers. I witnessed them down in Gilboa some few years back in great numbers, but still….not like the great numbers I remember as a child growing up on Long Island, where fields were aplenty in my hometown at one time. As the author relates above, everyone who has lightning bug experience says the same…. their numbers are far less.

    I would have never guessed that it would come so soon…this precipice we seemingly shrug off or have come to accept as the norm (if we are even aware at all!) Bees & butterflies are threatened, there’s a large decrease in bird populations, pollution is par for the course. Things are not what they used to be and until we change our thinking we will continue moving towards a catastrophic end thinks me. The disappearing of species are a large indicator of what’s to come….. and what are we doing about it!

  6. Cheryl Odell says:

    Great article. I see so many people with indoor gardens to help with the Monarch butterfly population. Is there anything like that to help the firefly population?

  7. Mike says:

    Worst thing to happen to insects: LED lights

  8. Rosemary Lee says:

    Thank you for writing this informative in the Adirondack we can see the night sky,however more and more outdoor lighting is being installed which are on all night
    please try and get your town to implement local ordinances to protect night sky and prevent damage to our insect and wildlife populations

  9. Charlie Stehlin says:

    “more and more outdoor lighting is being installed which are on all night”

    There has been discussions on this site regards attracting more people to the Dacks, people of all stripes, more diverse cultures, etc, etc…. and I recall me warning, “you might regret what you wish for”, or a specimen of that sort. I still stand by this! This ‘lights’ discussion is relative to such, as when you pull in more people from the urban areas, you pull in more of their urban habits. The urban folk just love their lit-up nights! Dark scares them, whether it be due to fear of criminal intent, or just plain old behavior patterns acquired over time and by experience. I suppose if economy wasn’t such a potent force in our thinkers we wouldn’t mind living in the Dacks just the way they generally have been until recently…..without the need for swarms of people filling up what once was empty, quiet space.

    Boxford, Massachusetts has a no street-light ordinance, or it was that way twenty years ago anyway….. I’m sure it still is. Them people in that small community like their dark nights. We miss out on so much due to all of the lights at night! And I mean this in more ways than one!

    • Boreas says:

      A good point Charlie. Another issue is year-round security lighting on dwellings that are only inhabited a few months of the year. Motion-controlled lighting needs to be much more prevalent than it is currently.

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