Nature’s Fireworks Display

This is a guest post by Sheryl Myers. 

Photinus Pyralis Source: Wikipedia
Photinus Pyralis
Source: Wikipedia

In the world of insects, few are more charismatic than the little beetles we know as lightning bugs. The most common species in our area is Photinus pyralis, the common Eastern firefly. On warm July evenings at dusk, a male in search of a mate will fly a few feet above the ground, flashing his cold yellow-green light to advertise his availability to females watching from nearby vegetation. A receptive female will respond with a single flash of her own. The time between flashes is species-specific, meaning that each species has its own characteristic flashing pattern.

Common Eastern fireflies produce a foul-tasting chemical that not all species of lightning bugs can produce. Predators, especially spiders, don’t like the bitter taste and tend to leave them alone. Fireflies belonging to a different genus, Photuris, are excellent mimics. Females from that genus can mimic the flash pattern of the Eastern firefly, then devour the male when he comes to mate. This femme fatale can then lay eggs that are protected from predators because they have acquired the foul taste of the male she just consumed!

Shortly after mating in late June and July, fireflies lay their eggs in the soil or under the bark of trees. The eggs hatch a few weeks later as carnivorous larvae and will feed for the rest of the summer on their favorite foods which include other larvae, snails, worms, and slugs. Some larvae can glow, and can be found glimmering with faint green or yellow light in moist roadside ditches, meadows, or woods. When the weather turns cold, the larvae will pupate to spend at least one winter in the soil. The cycle is completed when tiny fireflies hatch out of their pupae cases in spring or early summer.

The way lightening bugs produce their light has been copied by humans in the manufacture of glow-in-the-dark jewelry and SCUBA tank lights. Fireflies are able to combine luciferin with luciferase, which then produces a high-energy compound that emits cold light in a process called bioluminescence. Many marine organisms produce this kind of light in order to find each other in the dark. Individuals of some firefly species in the Smokey Mountain can flash simultaneously, drawing large crowds of admiring fans each spring!

Firefly populations are in trouble, and observers are reporting fewer sightings. The culprits seem to be habitat destruction and artificial lighting. Each year more natural areas are developed or plowed up for agriculture, and lightning bugs seem to disappear rather than migrate. Any bright outdoor lights can confuse and overpower the organic light signals that fireflies use to communicate with each other.

Catching lightning bugs is one of the special joys of childhood. Trapping them in cupped hands is fairly harmless, but putting them in jars is highly stressful and reduces their chance of survival. Loving them and leaving them is the best way to enjoy them!


About the Author: Sheryl Myers

Sheryl Myers taught biology and environmental science for 34 years and has worked as a naturalist for Anderson City Parks as well as Mounds State Park. She is a founding director of Heart of the River Coalition and a founding board member of Red-tail Land Conservancy.