Running around the backyard on summer nights in an attempt to catch fireflies is a fun pastime. These insects, also known as lightning bugs, can light up the night with their magical glow. But, what actually makes them flash?
Fireflies aren’t flies.They’re actually beetles. Fireflies are nocturnal members of the Lampyridae family. The name comes from the Greek “lampein,” which means to shine. Some fireflies are diurnal, but they typically don’t glow. Most fireflies are winged, which distinguishes them from other luminescent insects of the same family, often referred to as glowworms. The name “glowworm” can indicate many different species, including fireflies.
Fireflies are efficiency superstars.
Fireflies have light organs that are located beneath their abdomens. Although more than 2,000 species bear the name “firefly,” not all fireflies glow. Those that do mix oxygen with a pigment called luciferin to generate light with very little heat. The enzyme luciferase acts on the luciferin in the presence of magnesium ions, a chemical called adenosine triphosphate (ATP) and oxygen to produce light. The light that some fireflies produce is extremely efficient. In fact, it’s the most efficient light in the world! Nearly 100% of the chemical reaction’s energy becomes light. The light that fireflies produce may be green, yellow or orange in color.
Occasionally, fireflies put their efficient light to good use in flashy displays. Some fireflies, most famously in Southeast Asia, will synchronize their flashes. In the U.S., this phenomenon occurs during the first few weeks of June in the Great Smokey Mountains in Tennessee.
Firefly flashes can be as romantic as a dozen roses…sometimes.
Fireflies flash in patterns that are unique to each species. Each blinking pattern is used to help them find potential mates. Male fireflies typically fly through the air in search of a female by emitting a species-specific flashing pattern. Some fireflies only flash once, while others do so up to nine times. The females sit on the ground and wait until they see an impressive light display. They show their interest by responding with a single flash, timed to follow the males’ characteristic flashes in a species-specific manner.
Less romantically, female fireflies in the genus Photuris mimic the flash of females in the genus Photinus attracting Photinus males, which they lure in to eat. Not only do the Photuris females get food, they also incorporate chemicals from the Photinus males that make them distasteful to predators.
Fireflies use their light to ward off predators.Speaking of predators, firefly blood contains a defensive steroid called lucibufagins, which makes them unappetizing to potential hunters. Once predators get a bite, they associate the unpleasant taste with firefly light and avoid attacking the lightning bugs in the future.
Some fireflies eat other types of fireflies.
The larvae of most fireflies are predaceous, beneficial insects that feed on snails, slugs and worms. When they become adults, fireflies may eat pollen, nectar or nothing at all! The few species that remain carnivorous through adulthood eat other types of fireflies.
Humans are contributing to fireflies’ decline.
If you don’t see as many fireflies this summer as you have in the past, it’s because these lightning bugs are on the decline. Light pollution, development of fireflies’ habitats and harvesting are all leading to a decrease in the number of fireflies. When their habitat is overtaken, fireflies do not relocate. Instead, they just disappear.
If you live in a place where fireflies are common, look out for the patterns and habits discussed here. If you want to catch fireflies, keep them safe by placing a wet paper towel in the bottom of a glass jar. Pierce holes in the jar’s lid so that the fireflies can breathe. Don’t forget to release them after a day or two!