Summer is the perfect time to head out and enjoy the outdoors in Northeastern Pennsylvania. There’s nothing more memorable than those warm evenings, relaxing in the backyard until the fireflies start to glow.

If any creature represents summer, the firefly is definitely in the running. But what are these little bugs and how exactly do they light up the night sky? As the sun begins on a cozy evening, let’s see what really makes the glow.  

Believe it or not, the firefly produces one of the most efficient forms of light.

What are fireflies?

Fireflies, or lightning bugs, are not actually flies at all. In fact, they are soft-winged beetles and part of the Lampyridae classification.  These illuminating insects can be up to 1-inch in length and can be identified by their black wings and red detailing. 

Shockingly, some firefly species are diurnal, so they do not glow. Fireflies are omnivores, so they do eat both plants and other creatures. Some species consume nectar, while others eat nothing at all.  Though they can be toxic if eaten, these flying beetles are harmless to humans, and typically live for about two months. You can easily spot these beetles flying through the night in the backyard, a field, or other areas with plenty of greenery.

What makes fireflies glow?

Of course, the stand-out condition of the firefly is their glow. These beetles are capable of bioluminescence, a chemical reaction that occurs within their abdomen that creates that unmistakable glow. Through this reaction, they will emit a yellow-green light which they can control through their nervous system. 

Believe it or not, the firefly produces one of the most efficient forms of light. Using a combination of a chemical called luciferin mixed with luciferases enzymes and oxygen, they can produce light 100% of the time. While the most common light is yellow-green, these flying beetles can create yellow, orange, and green glows, depending on the species. 

Like their color variety, not all “glows” are the same. Fireflies use unique flash patterns, while others will synchronize their sparkle. With over 2,000 different species of firefly, there are plenty of distinct patterns to see.

Why do they only glow at night?

The whole goal of “the glow” is to catch the eye of a prospective mate. Night is the perfect time to flash those mating signals. During the evening, males will take to the sky in search of a mate. Using specific glowing patterns based on their species, the males will signal to the females. These signals can vary from single flashes, multiple blinks, or they can take very specific patterns. These crazy, night-time light shows are just one big mating dance.

As males fly, the females wait on the ground, watching for potential mates. Once they find what they are searching for, the females with return the flash signal back to the male if they want to mate.

It should be noted that not all fireflies produce at night. These beetles fly by day and use pheromones rather than flashes. 

Do they only come out in summer?

Like most insects, fireflies tend to prefer warmth over cool or cold weather. In fact, they’d prefer to avoid the cold altogether. Warm, humid weather is the most ideal climate for fireflies to thrive. Milder winter and wet springs are indications of an abundance of fireflies in the summer.

As cold-blooded insects, they depend on the heat. Unfortunately, a cooler summer could be bad news for fireflies.

The firefly glow is mainly used for mating.

That Glow is also a warning sign

While that glow is mainly used for mating, it takes on a secondary purpose. The bioluminescence works as a defense to ward off predators. Like other brightly colored creatures and insects, fireflies have a bitter taste when eaten. The beetles create chemicals called lucibufagins, which are toxins that can be deadly with a high enough dose.

While it may take a few lightning bug snacks before that toxicity level is fatal, they do taste awful, and those toxins come with a distinct smell. These defenses come mainly from the chemicals in their diet, and not all fireflies can create the chemical needed for these defenses. But that doesn’t mean they don’t have a work-around.

Females that cannot create the chemicals necessary can be little tricksters. After they’ve found their mate, they will remain in the grasses watching other insects. They will mimic the flash patterns of other females, lure males in close and eat them. After eating the unsuspecting mates, they take in the chemicals needed to protect themselves and their eggs. In addition, they will also bleed if a predator grabs them, leaving their would-be killer a nasty taste in their mouths.

Fireflies are fascinating insects, and it is truly a joy to watch them sparkle in the night. Their unique flash patterns and ability to create light is a wonder that, sadly, we are slowly losing. Due to increased light pollution, loss of habitat, and unpredictable weather, the firefly population is in a decline.  

Without a clear, darkfield or yard, it can be difficult for fireflies to find their mates. These glowing beetles don’t have the luxury of migrating to a new habitat; once they lose their space, the insects simply die off. If you want to keep these illuminating wonders and help them thrive, turn off the lights and enjoy the nighttime glow. Keep the summer tradition alive and well for years to come.


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