Imagine a late evening walk in mid June. The sun has just set, leaving behind the feel of the warmth of the day. A breeze gently rustles fresh green leaves that have become silhouettes of themselves. The faintest glow that the sun has left behind on the horizon has just begun to disappear. First one, then two, then three blinking lights floating through the air. Before you know it you're surrounded. All around, in the trees, the grass, the sky, fireflies dance gently in unexpected patterns, blinking in and out of existence. It feels like you've entered into some secret, magical place. A fairy garden where everything is just as it should be.
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| Fireflies and stars, mirroring one another. |
Those of us who are lucky enough to have experienced this know how impactful it can be. Fireflies have always captured human awe and imagination. They are like living stars on earth, and just like the stars themselves, they are beginning to go dim. Where I live, fireflies are most active in June and July. We have moved into August now, and I haven't seen as many as I used to. Studies by the Xerxes Society indicate that firefly populations are indeed in decline, and that at least one species of firefly is in danger of extinction. So let's take a look at these fascinating creatures, and then at a very simple way that each and every one of us can ensure that it survives.
*Skip ahead to the next asterisk if you're here for the wonders of nature and conservation tips, not the icky bug stuff.
There are about 2,000 known species of firefly, and each is unique. Adult firefly eating habits are a good way to see just how different these species can be from one another. Some simply sustain themselves with pollen. Others cleverly stake out spider webs. Then, when the time is right, they battle the spider for its neatly wrapped to-go style meal. One species in particular has a rather disturbing dining habit. The females of this species mimic the flash pattern of smaller firefly species, tricking unsuspecting males into coming closer. When they do, they are quickly trapped and eaten by the larger, trickier firefly. In contrast, some species of firefly eat nothing at all once they reach their adult form.
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| The Photuris Firefly, known as the femme fetal of the bioluminescent world |
* Okay, you're safe. Please come back! Thank you for sticking with me <3
Fireflies are most famous for their glow, or bioluminescence. It's probably the reason they strike so many of us as magical rather than just another freaky beetle. But fireflies don't glow just to entertain and inspire us. While we don't know everything about firefly behavior, one thing is clear. Fireflies use their lights for mating communication. Scientific observation, documentation, and research on firefly behavior is not yet robust enough to rule out other topics of conversation hidden in their flash patterns. One phenomenon that has now been officially observed and documented, but is yet to be understood is the synchronization of entire fields of fireflies in places like the Great Smoky Mountains National Park. There is more than one mystery here. How, mathematically, can these fireflies coordinate their synchronized light show? Why? What biological benefit could this type of broad cooperative behavior have? Or are they, in human terms, simply making music?
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| One species known to exhibit synchronizing behavior is Photinus Carolinus. |
I was surprised to learn that it's not just adult fireflies who glow. Many species of firefly have bioluminescent capabilities during every stage of life. This means that when disturbed, even their eggs can glow.
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| Glowing firefly eggs. |
Fireflies and their glow have even helped to save human lives. The enzymes that cause their bioluminescence have various medical applications, including an effective process for detecting blood clots. At this point, humans have managed to artificially replicate the enzyme, but we used to get it directly from fireflies.
We still have more to learn from them. Fireflies are more efficient at producing light than humans are. Even with the advent of fluorescent light bulbs, about 90% of energy from artificial bulbs is released as light, leaving 10% to be released as heat. Fireflies produce light at 100% efficiency. And it turns out that light is exactly the issue. We live in a world of ever increasing light pollution. This really doesn't sound like a big deal, until we start to look at the scale of the impact it has. The excessive lighting used in and outside of cities has caused "sky glow." This means that most stars are obscured by the light of human civilization reflected back on itself. According to National Geographic, 80% of Americans can no longer see the milky way dusting across the night sky. Those of us who were born and raised in cities might not even realize what we were once able to see in the sky on a dark starry night.
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| Nasa's visual representation of sky glow for stargazing reference. |
Since the natural night and day lighting cycle has been foundational in the development of life on earth, it is likely that all living things exposed to excessive light during the night are adversely effected in ways we do not yet understand. We've already found that several animals are directly affected by the lack of a dark night. Humans rely on the absence of blue light at night to produce melatonin and have healthy sleep. Frogs rely on the dark hours of the day to know when to begin their chorus of croaking, the disruption of which prevents them from mating. Perhaps even more sad is the way that sea turtles can be affected by unnatural light. According to the World Wildlife Fund, nearly all species of sea turtles are now endangered. Newly hatched sea turtles head straight for the ocean, using the light of the bright horizon between water and sky to guide them. Unnatural lights can confuse them, causing them to crawl away from the safety of the water. The International Dark Sky Association claims that, due to light pollution, millions of hatchling sea turtles die on the Florida coastline every year.
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When shopping for outdoor lighting fixtures, look for the |
Consider what we know about the firefly, combine that knowledge with the effects of light pollution, and you will realize how devastating artificial light can be for fireflies. A nocturnal creature using its glow to attract mates has no chance of mating at all when it finds itself living in a well lit night.
For many species affected by light pollution, research has shown that the colour of light makes a huge difference. Humans who avoid blue light before bed, for example, tend to get a better night's sleep. Red or yellow light tones (long wavelengths) are generally healthier than blue light tones. The firefly itself has a wide range of light tones. Some species glow blue, some green, others orange or yellow. Is it possible that taking advantage of the broad spectrum of light available to us and focusing our outdoor lighting away from blue tones could make a difference? For many creatures, yes! Unfortunately, this rule of thumb does not apply to fireflies. A study conducted at Tufts University last year, found that no colour of artificial light is unharmful to fireflies, and that amber light (which for many creatures is most helpful) might actually be the worst for fireflies.
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| Firefly with yellow glow |
The good news is that there are still some very easy things we can do to help these fascinating creatures. Something as simple as turning outdoor lights off at night when they are not in use, or closing window blinds after the sun goes down is all it takes to improve the fireflies chance of survival. Every little bit counts. You or someone you know may already have outdoor lighting set to motion sensors or timers, so that they are only lit when they're in use. This is a great way to save on the electric bill, but the fireflies are thankful for it, too!
I think it's exciting to hear how much we can help in little ways that don't even inconvenience us. If only every act of conservation were so easy. A lot of the lighting we use is inefficient. Pay attention to billboards the next time you're driving at night. Unless you live in an area where billboards are regulated to decrease light pollution, you'll likely see that the lights used to illuminate them are pointed straight up from below. This means that light is being directed at the sky and diffusing away from the billboard. The simple switch of pointing billboard lights downward instead would decrease light pollution drastically. It's all about being just a little bit smarter than we were yesterday. The same line of thinking applies to lighting outside people's homes and businesses. Intentionally directed, shielded lighting ensures that lights are effective where we need them to be, and allows wildlife to coexist with us.
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Shielded lighting has the added benefit of avoiding the decrease in dark vision that unshielded lighting often results in for humans. |
This resource from the Xerxes Society has great information on how to minimize your light pollution impact on fireflies (note that some of the information regarding light colour is outdated).
Thank you for taking the time to consider the fireflies. A little mindfulness about our effect on other creatures goes a long way.
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