Fireflies: Why Do Fireflies Glow?

Lightning Bugs Facts and How to Attract Them

By George and Becky Lohmiller
June 4, 2020

Fireflies light up a forest night. Why do fireflies glow?

University of Florida

Fireflies—also known a lightning bugs—have been captivating humans for centuries with their beautiful lights on summer nights. What makes fireflies glow the way they do?

The nearly 2,000 species of fireflies worldwide inhabit every continent except Antarctica. The firefly isn’t actually a fly at all, but rather a beetle from the family Lampyridae, which in Latin means “shining fire.” This “fire” that makes fireflies so fascinating is really a method of communication for the insects.

What’s most fascinating is that this living organism can produce light (called bioluminescence) which is relatively rare. And they form a beautiful language with light (as opposed to many animals’ languages of sound and scent). What signals are they sending? Let’s explore …

How Do Fireflies Glow?

Photocytes, or light cells, in the insect’s abdomen are where the glow is produced.

This light, the result of the chemical reaction of bioluminescence, occurs when two substances, luciferin and luciferase, react with one another when exposed to oxygen. The firefly regulates the flow of oxygen into its abdomen, which allows it to turn its taillight on and off.

This cold, living light is almost 100 percent efficient, losing only a fraction of its energy to heat. By comparison, a standard incandescent light bulb is less than 10 percent efficient, and an LED ranges between 40 and 50 percent efficient!

Why Do Fireflies Glow?

The main purpose of a firefly’s light show is to attract a mate. The males fly around while turning their lights on and off, hoping to get the attention of a flightless female waiting in low vegetation. They try to flash very quickly, because this is what attracts females.

If a female is impressed by a male’s flickering, she will flash back a response to the twilight glow. The brighter the female’s response, the more interest she has in the male. 

Each species of firefly has its own unique flash that is characteristic of its sex and species. Carnivorous females of the genus Photuris are known to entomologists as “femmes fatales.” These fireflies mimic the flashes of females of other firefly genera; the unsuspecting courting male flies in (expecting romance) and is promptly eaten.

A firefly’s light can also serve as a warning to predators. In the same way that bees scream “Danger!” with their black and yellow stripes, fireflies show their toughness with their light. Fireflies even have an advantage over bees, because their warning can be seen in the dark!

Photo Credit: Wesleyan University. Fireflies are often found in meadows or next to creeks, as they like damp areas.

How to Find Fireflies

Fireflies are most abundant in the eastern half of the continent, from Florida to southern Canada, but different species can be found anywhere in North America.

  • They like meadows and marshes and fields and prefer cool, damp, dim conditions.
  • They rely on that habitat remaining undisturbed for the year or more it takes them to complete their life cycles which is why their habitat can easily disrupted by logging and development. Unfortunately, many wingless species can’t disperse any further than they can walk, so they can’t easily re-establish. Habitat destruction is one of the greatest threats to fireflies.
  • Try to find an area with very little light pollution: a meadow, the edge of a forest, or even your backyard if you don’t live in an urban area. Also, keep the outdoor lighting at your home dim.
  • Go out to look for fireflies soon after sunset. If you stand still and watch carefully, you just might see a few!
  • Fireflies don’t come out until the warmth of spring, so wait until the spring and summer months of May, June, and July to search for them.

One downside to firefly watching is that mosquitoes also like the same conditions. Unfortunately, some common methods of deterring mosquitoes (like using a pesticide) also kill fireflies and are another reason for their decline.

How to Attract Fireflies

The best way to attract these blinking bugs is to turn your yard or garden into the ideal firefly environment:

  • Fireflies appreciate shrubs and low trees for daytime shelter, so consider planting some to keep them around.
  • Fireflies like to hang out in grassy meadows, so if you want them to visit your property, let some parts of your lawn grow out or plant tall ornamental grasses. They enjoy perching on the tips of long blades of grass while searching for a mate. 
  • Place bird baths in grassy areas or near shrubs; fireflies will appreciate the water source. 
  • Don’t use mosquito-repelling chemicals in your garden, as these will also repel fireflies.

More Fun Firefly Facts

  • Fireflies taste horrible to predators like birds and mice. They release a bitter defensive chemical when eaten, which helps to keep predators away.
  • All fireflies are bioluminescent as larvae (which is why the larvae are often called glowworms), but not all of them shine as adults. The fireflies that lose their ability to make light use scent to find mates instead.
  • Even though a firefly’s light is triggered by oxygen, fireflies do not have lungs. Instead, they inhale oxygen through tubes called “tracheoles.”
  • A lightning bug’s flash can be yellow, green, or even blue!
  • Fireflies are only about ½ inch long, and they have very big eyes so that they can see the flashes of other fireflies.
  • Fireflies (as well as their larvae, glowworms) help to control garden pests like snails, slugs, cutworms, and aphids, so be sure to keep them around if you have them in your garden.

Photo Credit: Clemson University. It is important to protect beneficial firefly populations, so be sure to release them from jars.

Though many people love to catch fireflies in jars and keep them around, fireflies can be much more beneficial in your yard than in your house. Even if you keep them in a jar for a few hours, be sure to release them again. And for the effect of putting lightning bugs in a jar without bothering any of them, try our Mason Jar Lid with Star Lights.

Let your love light shine with these dazzling garden friends, and let us know in the comment section if you’ve found lightning bugs in your garden!


This page was first published in 2010 and has been updated.


Reader Comments

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Fireflies in garden

Article was very informative on how fireflies light up and attract mates, but I didn't see any info on how to attract them to your garden. Did I miss something?

Attracting Fireflies

The Editors's picture

We do offer a few tips on attracting fireflies above, such as planting shrubs and trees, as well as keeping your outside lights dim (or off) and not using mosquito-repelling chemicals. We’ve created a new section to make this information easier to find!

The best way to attract fireflies is to make your yard and garden into their ideal environment: They appreciate long (at least knee-high) grasses, as well as low shrubs—anything that acts as a good shelter, essentially. They’ll also appreciate bird baths as a water source.

skeeter truck killed em!

When I first moved here I use to love to go sit out back after dinner and watch the fireflies. Get that peaceful feeling only nature could bring. Then the road got paved, and the mosquito truck started making its rounds and after a couple of seasons, they are no more. Completely devastated the population, but the dang skeeters survive. I live in Florida and the pests seem to really like me, and without the trucks running around they almost come in swarms. Shame there isn't a viable solution to riding us of skeeters and keep the fireflies. I do miss them. :{

Losing Fireflies everywhere

Pollution is killing everything, I once had hundreds of fireflies in my backyard but now I am down to a couple dozen on a good night. I don't spray, use organic gardening practices, provide cover, food and water for all my critters yet every year I have less and less fireflies, less butterflies, less everything, so sad how we humans are destroying the earth and all it's beautiful creatures.


We live in Washington State and have seen what we assume are fireflies up in the trees. Do fireflies come this far west

Firefly geography

The Editors's picture

The most commonly-known fireflies live in the Northeast and Midwest. You commonly see them flying across meadows and lawns. Fireflies are less common as you go west, however, because they prefer humid environments. The ones you do see tend to be smaller and their glow is more faint. However, there are MANY species of fireflies and 18 in California alone so they do exist!

Fire Flies

1 of your Comments claimed to have seen them in Washington State and your Staff says there are 18 Types in California. I’m not sure I Believe that. As I mentioned in my Comments - I lived in California for 52-53 Yrs. NEVER saw Any.
Just Exactly Where Are They in California Or Coeur d’Alene, Idaho ? I’ve been told they don’t come this far West or That far North. Who’s Right ?
Not Criticizing - Just Bummed That I’ve Never Seen Any.

Fireflies in CA?!?!? Need More Details.

With my childhood spent in Ballwin, MO, I miss fireflies marking summertime being in Southern CA now. I speak of those evenings still to this day. Huge weeping willow trees sprinkled with sparkles. I even wished we could FedEx some larvae out here in jest. Which ones are out here?!?! Please elaborate and if that is factual, what can we do to help populate out here in CA? I’ve never seen one in CA.

No fireflies in WA state

I've lived all my life in WA state and never saw any lightening bugs. Visiting my mom's family in Kansas as a child, I saw them ( and learned what a REAL lightening storm was! ) but they don't live in WA state...or if they do, I'd sure like to know where.

I'd like to see them again before I die!


Love watching the fireflies when they start "blinking" at sunset, but notice there are fewer and fewer of them each year.

Your Firefly Article

The last time I was fortunate enough to personally see fireflies was on the 4th of July, 8 years ago. I was in a very marshy area a half mile away from the town firework show...fewer people, less traffic..old dirt road. Then I seen them. I swear, the joy that swelled within me made me downright giddy. My daughter was 4 and she was just as amazed. It was quite the experience, even better than fireworks....sadly, for us, the mosquitoes found every inch on us that we missed with the repellant and we were only able to tolerate 2hrs of happiness. I can't really make my proerty firefly friendly by adding watersources, heck, I had to put plants in my stone birdbaths because the mosquitoes breed so profusely. It's a shame. I loved the article though...maybe someday. Closing on a positive note, I have become a milkweed junkie and strive to release as many Monarch Butterflies as possible yearly. Aphids are no match fo me. I dab q-tips in Alcohol and dab the aphids. Dead in minutes. Keep spreading the joy of fireflies!!


We saw fireflies in February here in Mississippi. While they may taste bad to birds and mice, apparently not to bats as we have seen them eat the fireflies in flight. Stinking ole bats!


I like watching them as in the early evening, they start around ground level. But as it gets darker, they'll "Congregate" up in the trees. Then they look like the LED lights for Christmas trees flashing up in the trees. I never did like the lights to stay on, but I liked when they flashed. And at times, there were so many, it looked like the entire trees were just flashing constantly. They are beautiful and fun to watch, and NO, I don't catch them and put them in jars ANYMORE. haha


In NE San Antonio, TX, the last two springs (2016, 2017) have brought us clouds of fireflies! It has been enchanting partly just to sit outside to watch them and partly to sit and remember chasing them as a delighted (and determined!) child. The winters those years were mild and a little wetter than others which may have been helpful. (Note, most of the yards in my neighborhood use little, if any, toxins on the yards - also helpful.)


Still see a few each summer in our back yard that backs up to a rather dense area of woods. Not nearly as many as years ago. We love watching them and wish there were more.


I live in Texas. In some areas the light is in their tail, and in others their head. I love to watch for them on Summer nights. Very peaceful.


very nice article, thanks a lot