Fireflies – Glow with the Flow
Common Eastern Firefly, Flickr,

Written by: Shelby Paxton

If there is one thing fireflies are known for, it’s their ability to glow. In fact, some of my fondest childhood camping memories have involved watching the soft yellow glow of fireflies blink through the woods as my family and I sat around a campfire. But what are they beyond their blinking lights and how do they even produce light?

Firefly Glowing, Flickr,

First off, despite being called a ‘fireFLY’, fireflies are actually a type of beetle [1]. The reason for this is that their hindwings are hardened into a tough case known as elytra and they have 2 pairs of wings while flies only have 1 pair [2]. Another key trait of beetles is that they go through a process known as complete metamorphosis, this means that beetles look different in each life stage (larva vs. adult), and generally each life stage has a different diet [3]. The firefly is no different, the larva resembles an armoured grub and feeds on other invertebrates while the adult tends to feed on nectar [1].

Common House Fly, Flickr,


Common Eastern Fire in Flight, Flickr,
Firefly Larva, Shelby Paxton

Firefly larva vary in how they live, some are terrestrial, subterranean, or even aquatic [4]. Of the invertebrates they feed on, snails are their preferred prey [5].

Lets talk about how fireflies create their signature glow. It’s all thanks to a chemical reaction that occurs in their abdomen that involves oxygen, ATP, luciferin, and an enzyme known as luciferase [4]. This reaction is efficient, almost 100% of the energy is given off as light while 90% of energy of incandescent lightbulbs is emitted as heat [4, 5]. All life stages of fireflies can glow as well, including the eggs except for a few firefly species who stop glowing when they reach adulthood [5]. Some other beetles are also capable of glowing such as click beetles [5].

Pyrophorus noctilucus, Wikimedia Commons,

But why do they glow? As you might have guessed, it’s a big ol’ mating display. Males flash their lights to reach out to females who will flash in response [5]. On top of that, each subspecies of firefly has their very own light pattern that they use to attract mates [1]. Glowing does have a couple of other uses, it warns predators of their foul taste and some female fireflies mimic the blinking pattern of other firefly species to capture and feed on males [6].

Want to attract fireflies to your yard? Fireflies are attracted to tall grasses and shrubs [7]. Examples of native plants you could grow are Big Bluestem, Indian Grass, Switchgrass, Serviceberry, Chokecherry, and Eastern Redbud [8]. Fireflies also like moisture so having a small pond will bring them to your yard, however, it may attract mosquitos as well [7].

Tall Grasses

Big Bluestem, Flickr,
Indiangrass, Flickr,
Switchgrass, Flickr,


Serviceberry, Flickr,
Chokecherry, Flickr,
Eastern Redbud, Wikimedia Commons,

Unfortunately, the future is not looking so bright for fireflies, firefly populations are decreasing due to loss of habitat, and climate change [5]. Another major reason behind their decline is that people have been collecting wild fireflies for their luciferase [9]. Luciferase is used by scientists as markers for blood clots, viruses, and to monitor hydrogen peroxide in living organisms [5]. Fortunately, a synthetic luciferase has been developed which has decreased the firefly harvests [5]. If you would like to help out fireflies, think about participating in Mass Audubon’s Firefly Watch, where you can report sightings or lack of sightings of fireflies to track their populations. Learn more about the watch here:

Common Eastern Firefly, Shelby Paxton
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