When is a Fly Not a Fly?

Fireflies are not flies. They’re also called lightning bugs, but they’re not true bugs either. Instead, fireflies are a type of beetle. In North America there are more than 270 species; worldwide there are more than 2400 species.

Fireflies are found on every continent except Antarctica and live in parks, meadows, gardens, and the edges of woodlands. Larvae eat snails, worms and slugs, while adults eat other fireflies (!), nectar, or pollen, if they eat anything at all.


When You Gotta Glow, You Gotta Glow

Luciferin, an organic compound in the firefly’s abdomen, undergoes a chemical reaction with the air that enters the abdomen, resulting in the familiar summertime glow that is called bioluminescence. Firefly larva, aka glowworms, are also bioluminescent, but do not have wings. The eggs of some firefly species also glow, flashing in response to vibrations or gentle tapping.

Firefly larvae use light to deter predators, though some species lose the ability to produce light when they reach adulthood. Some of the many different firefly species use flashes to attract mates, while others use light to attract prey. They also use flashes to defend territory and warn predators away.

Both males and females glow. Often the male will fly while females will wait to spot an attractive male, which she will signal with a flash of her own.

Bioluminescence in fireflies is nearly 100 percent efficient. Compare that to the incandescent light bulb’s 10 percent efficiency. But you’d need more than 2000 fireflies to make the same amount of light as a 60 watt bulb.

While adult fireflies typically live for a couple months, they don’t last much more than a day if an eight-year-old has trapped them in a jar so she can read by their light late at night. Ask me how I know.

How to Attract Fireflies to Your Yard

Most firefly species need standing water. They don’t need a lot; small depressions or vernal pools suffice. They like humid, warm environments, which almost perfectly describes a Baltimore-area backyard in the summer.

Fireflies also like long grass. During the day, they spend most of their time on the ground, where long grass provides cover until darkness falls and they fly into tree branches to signal for mates.

So if you mow, mow high, and provide a water source. Then enjoy the soundless glow on a hot summer night.