Fireflies may be our most beloved insects, but we know surprisingly little about them. Fortunately, what we do know about fireflies is fascinating. Here are 10 cool facts about fireflies.
1. Fireflies, also called lightning bugs, are neither flies nor bugs.
Fireflies are actually beetles. Like all other beetles, they have hardened forewings called elytra, which meet in a straight line down the back when at rest. In flight, fireflies hold the elytra out for balance, and rely on their membranous hindwings for movement. These traits place fireflies squarely in the order Coleoptera.
2. Fireflies are the world's most efficient light producers.
Have you ever touched a light bulb that's been on for a while? If you did, you probably burned your finger! An average electric light bulb gives off 90% of its energy as heat, and only 10% as light. If fireflies produced that much heat when they lit up, they'd probably incinerate themselves. Fireflies produce light through an efficient chemical reaction that allows them to glow without wasting heat energy. All 100% of the energy goes into making light.
3. Fireflies "talk" to each other using light signals.
Fireflies don't put on those spectacular summer displays just to entertain us. You're actually eavesdropping on the firefly singles bar. Male fireflies cruising for mates flash a species-specific pattern to announce their availability to receptive females. An interested female will reply, helping the male locate her where she's perched, often on low vegetation.
4. Fireflies are bioluminescent throughout their life cycles.
We don't often see fireflies before they reach adulthood, so you may not know that all stages of the firefly glow. Bioluminescence begins with the egg, and is present throughout the entire life cycle. In fact, all firefly eggs, larvae, and pupae known to science are capable of producing light. Scientists believe that larvae use the light to warn predators away, but we don't know this for certain. Some firefly eggs will emit a faint glow when disturbed.
5. Not all adult fireflies flash.
Fireflies are known for their blinking light signals, but not all fireflies flash. Some adult fireflies, most notably those that inhabit the western areas of North America, don't use light signals to communicate. Many people falsely believe that fireflies don't exist west of the Rockies, since flashing populations are rarely seen there.
6. Firefly larvae feed on snails.
Firefly larvae are carnivorous predators, and their favorite food is escargot. Most firefly species inhabit moist, terrestrial environments, where they feed on snails or worms in the soil. But a few Asian species use gills to breathe underwater, where they feed on aquatic snails. Some species are arboreal, with larvae that hunt tree snails.
7. Some fireflies are cannibals.
We don't know much about what adult fireflies eat. Most don't seem to feed at all, while some are believed to eat mites or pollen. We do know what Photuris fireflies eat, though – other fireflies! Photuris females enjoy munching on males of other genera. How do they catch their lightning bug cousins? See fact #8.
8. Female fireflies sometimes mimic the flashes of other species.
The well-known femme fatales in the genus Photuris use a trick called aggressive mimicry to make meals of other fireflies. When a male firefly of another genus flashes its light signal, the female Photuris firefly replies with the male's flash pattern, suggesting she is a receptive mate of his own species. She continues luring him in, closer and closer, until he's within her reach. Then she eats him!
9. Firefly luciferase is used in all kinds of medical research.
Scientists have developed remarkable uses for firefly luciferase in the research lab. Luciferase can be used as markers to detect blood clots, to tag tuberculosis virus cells, and to monitor hydrogen peroxide levels in living organisms (hydrogen peroxide is believed to play a role in the progression of some diseases, like cancer and diabetes). Fortunately, scientists can now use a synthetic form of luciferase for these research purposes, as the commercial harvest of fireflies could put our native species at risk for population decline.
10. Some fireflies synchronize their flash signals.
Synchronous fireflies are one of the seven wonders of the insect world, in my opinion. Imagine thousands of fireflies lighting up at precisely the same time, over and over, from dusk to dark. This simultaneous bioluminescence, as its called by scientists, occurs in just two places in the world: southeast Asia and Great Smoky Mountains National Park, right here in the U.S.A. North America's lone synchronous species, Photinus carolinus, puts on its light show in late spring each year.