Many backyards are already aglow with magical fireflies – or lightning bugs, as many people call them. On warm evenings, there’s nothing better than sitting and watching them light up the night. Here are a few facts you may not know about these fascinating insects:
It turns out that it’s not just the adult fireflies that light up. Among some species, the eggs glow, and the eggs of certain species will flash if you tap them gently. Most firefly larva – often called glowworms – are also capable of producing light.
No man-made light source can claim to be entirely energy efficient, but a firefly’s glowing tail uses 100% of the energy it produces to emit light. By comparison, the average incandescent lightbulb releases 90% of its energy as heat and 10% as light, while fluorescent bulbs release 30% as heat and 70% as light.
The flashing is more than just a pretty light show. Among the species of fireflies that produce a glow, each one has its own unique flash pattern, and they use the flashes to attract mates. Females wait in tall foliage, flashing to attract males. The males flash in response as they move closer to the females. The glow is also a handy way to repel predators. Since fireflies produce bitter chemicals as a response to predators, most insect-eating animals know that if it lights up, it tastes bad.
It’s easy to identify fireflies by their flash patterns. Photinus pyralis is one of the more common types found in the United States, and this species always makes a J-shaped flash by lighting up as they fly in an arc. Photinus brimley flies in a straight line and produces one flash every three to eight seconds. Photinus consimilis makes a double flash every five seconds, and Photinus collustrans flashes three times in two to three seconds.
Some fireflies are tricksters. While adults of most species eat pollen or smaller insects, some females of the Photuris genus prey on male fireflies of other species. They’ll lure the males in by mimicking their flash patterns. And, since female Photuris fireflies gravitate towards the flash patterns of different species, male Photuris fireflies mimic those species to attract the females.
Most people recognize fireflies by the greenish light they produce, but not all fireflies make yellow or green light. Pyractomena fireflies, for instance, create orange light. In the southern United States, you may chance across Phausis reticulata, or the Blue Ghost firefly. Blue Ghosts don’t flash at all, instead they produce a soft but steady blue glow. Other fireflies, particularly those that live in the western United States, don’t light up at all.
Some fireflies can actually synchronize their flashes. In the United States, there is only one synchronous species – Photinus carolinus – and there are only a few spots to watch as they put on one of nature’s greatest light shows. You can catch a glimpse in the Allegheny National Forest in Pennsylvania or the Congaree National Park in South Carolina. The best place to watch, however, is the Great Smoky Mountains National Park in Tennessee. People flock to this park every May and June to watch as thousands of fireflies produce perfectly timed flashes.
Fireflies glow because their tails contain just the right chemicals and enzymes (calcium, adenosine triphosphate, luciferin and luciferase) to create a bioluminescent chemical reaction. These insects control the flashing by adding oxygen to start the chemical reaction within the light-producing organ in their tails.
Fireflies help save lives. Researchers have discovered that the luciferase produced by fireflies is useful for anything from detecting blood clots to tracking the efficacy of cancer medications. In fact, scientists have learned how to make synthetic luciferase, which means that the medical industry no longer needs to harvest this bioluminescent chemical from fireflies.
Fireflies have surprisingly short life spans – only one season. They spend most of their adult lives searching for a mate. Once mated, the females lay their eggs and die shortly thereafter. New crops of fireflies hatch the following spring and the cycle starts over!