When do fireflies glow in their lifetime?

When do fireflies glow in their lifetime?

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Does a firefly glow only when adult or larva? Or does it glow during its whole life. By glowing, I mean that they glow only when they require, not all the time.

Is there a reason (evolutionary reasoning) why they glow? Also, if the answer is all the time, then why, or if the answer is specific period in life then why?

Fireflies 'glow' in larval and adult stages but for very different reasons. It is thought that glowing behaviour first evolved in larvae to deter predators(Branham and Wenzel (2003)). This is an example of an aposematic warning, which uses bright colours, smells, sounds, or in this case light, to tell predators they are undesirable as prey. Sometimes a prey animal will use an aposematic warning to tell predators they are poisonous, or simply to mimic a prey that is poisonous. In the case of firefly larvae, they don't taste good to predators because of a steroid compound in their bodies (Branham (2005)).

Adults also glow, but do so in a synchronized pattern of flashes to communicate with mates (Carlson and Copeland (1985)). Mates will time their flashing with physiological fluctuations and even respond directly to another individual's flashing pattern with appropriate delays and timing of responses.

So to answer your first question, fireflies are not continuously glowing, but flash at night as larvae to deter predators, and during active mating as adults.

Your second question can get into a long-winded explanation of how certain traits evolve in response to a pressure, but to simplify, it's likely that fireflies evolved glowing because it relieved predation pressure. This ability then evolved further to communicate the quality of mates more efficiently than phermone signalling.

When do fireflies glow in their lifetime? - Biology

Scientific Name: Photuris pennsylvanicus
Common Name: Pennsylvania Firefly

(Information in this species page was gathered in part by Ms. Megan McAuley for an assignment in Biology 220W (Spring semester 2007)).

The Pennsylvania firefly (Photuris pennsylvanicus) (also called the &ldquoLightning bug&rdquo) is a cherished feature of warm Pennsylvania summer evenings. Its pulsing pinpoints of yellow and green light make the dark woodlands, fields, and gardens come alive with movement and possibilities. The firefly was named the state insect of Pennsylvania in 1974.

Classification and Appearance
The &ldquofirefly,&rdquo though, is not really a fly at all. It is a beetle in the family Lampyridae that, along with several hundred other closely related &ldquofirefly&rdquo species, has the remarkable ability, in all of its life stages, to biologically generate light. The adult beetle, which is the form most familiar to people, is ½ to ¾ inch in length, with a flattened body that is predominately black in color with yellow highlights and prominent red spots on the back of its thorax. It has large eyes and long antennae and flies in a gentle, hovering manner. The light generating parts of these adults are in the terminal segments of their abdomens. The adult firefly has long, curved mandibles that suggest a predaceous life style, but only a few species have been shown to actually consume anything other than flower nectar or pollen. The less well known larvae of the firefly, called &ldquoglow worms,&rdquo live in leaf litter and are voracious predators. They eat other insects, mites, earthworms, and even slugs and snails.

Using Light for Communication
The lights of the fireflies represent communication mechanisms. The female fireflies, which are predominantly sessile, perch on the vegetation in its habitat and generate a species specific sequence of light flashes that attract the much more mobile males. The males respond with an answering light sequence and zero in on the females in order to mate. A few species of firefly have been shown to mimic the light sequences of other species in order to draw unsuspecting males to waiting, predaceous females. These females not only gain energy from consuming the males of these other species but also can accumulate chemicals from their prey which help to protect them from their own predators. This behavior is called &ldquoaggressive mimicry.&rdquo

After mating in the late summer, the females lay their eggs one at a time on the surfaces of woody or leaf debris. The eggs hatch in a few weeks and the emerging larvae enter the soil/litter habitat where they actively feed on a wide range of invertebrates. In late fall, the larvae burrow into the soil or under the bark of woody stems where they overwinter. In the spring, they re-emerge and continue to actively feed on their diverse array of prey species. After a few weeks, they re-enter the soil and pupate. They then emerge from their pupal chambers in early to mid summer as adult fireflies.

Light Production
The mechanism for the production of light in fireflies is mediated by the enzyme &ldquoluciferase.&rdquo High energy phosphates generated from food molecules are coupled via luciferase to the direct production of photons of light. This coupling is extremely efficient (90%+) and generates almost no waste energy (heat). The genes that regulate this light generation have been used in cancer research to mark and track metalizing cancerous cells.

There have been many reports of declining numbers of fireflies throughout North America. The widespread use of pesticides and herbicides, the loss of the leaf litter habitat required by larval life stages especially in suburban areas, and drought have all been proposed as factors in the decline of the firefly. It is hoped that this decline can be reversed so that we can all continue to have the pleasure of observing these unique and wonderful organisms.

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The Science Behind Fireflies

Running around the backyard on warm 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? Read on to learn about the science behind this dazzling summer bug. You might be “enlightened!”

Fireflies aren’t flies at all!

They’re actually beetles. Fireflies are nocturnal members of the Lampyridae family. The name comes from the Greek “lampein,” which means to shine. Oh, the irony! 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. Talk about a strange diet!

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!

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Fireflies eat other fireflies.

Fireflies are primarily carnivorous. Larvae usually eat snails and worms.
Some species of fireflies feed on other fireflies—most notable is the
genus photuris, which mimics female flashes of photinus,
a closely related species, in order to attract and devour the males of
that species. But adult fireflies have almost never been seen feeding
on other species of bugs. Scientists aren’t sure what they eat. They may
feed on plant pollen and nectar, or they may eat nothing.


Fireflies mostly use their light to “talk” to other fireflies and find a mate. They have special organs under their abdomens that take in oxygen. Inside special cells, they combine the oxygen with a substance called luciferin to make light with almost no heat. They use this light, called bioluminescence, to light up the ends of their abdomen.

Each firefly species has its own unique flashing pattern. When a male firefly wants to communicate with a female firefly, he flies near the ground while he flashes his light every six seconds. Once he’s near the ground, a female can more easily tell if he’s from the same species as she is. (Most female fireflies can’t fly.) She answers his flashes by turning on her lights. Then the male finds her.

Predators, such as birds or toads, get a different message from these lights. Although they can easily spot fireflies by their glow, they rarely eat them. That’s because fireflies release drops of toxic, foul-tasting blood. Their flashing is a warning light to predators to stay away.

How Fireflies Light Up Their Bodies

The secret trick by which fireflies are able to light up all starts in their abdomen. Fireflies contain a special light-emitting compound in their abdomen called luciferin. When luciferin and a particular enzyme, luciferase, react with oxygen, a chemical reaction occurs. This reaction releases energy in the form of light, thereby lighting up the firefly&rsquos body. The wavelength of light emitted by fireflies is in the range of 510-670 nanometers (pale yellow to reddish-green).

Firefly (Credits:Tyler Fox/Shutterstock)

The light generated by a firefly is called &ldquocold light&rdquo, as the heat generated is very minimal. This is good for the firefly, as its body would not be able to survive if it generated heat like a light bulb. The process through which fireflies light up their bodies is called bioluminescence. A firefly is not the only creature who has this ability, however many other organisms, mostly sea and marine organisms, can also produce their own light.

The enzyme that turns on the rainbow of colored lights that occur in different firefly species is called luciferase. Sara Lewis, author of the beautiful new book Silent Sparks: The Wondrous World of Fireflies, says what first hit the switch was really a glitch.

The firefly gene that codes for luciferase is very similar to a common fatty acid-making gene, Lewis says. It's likely a duplicate of that gene acquired a mutation that caused it to produce a tiny bit of light in a distant firefly ancestor. (Related: How Do Fireflies Glow? Mystery Solved After 60 Years).

Over eons high concentrations of that light-producing chemistry evolved along with specialized tissue, to create a whole new “light organ,” Lewis says—the firefly lantern.

Bioluminescent beetles

Fireflies produce light in special organs in their abdomens by combining a chemical called luciferin, enzymes called luciferases, oxygen and the fuel for cellular work, ATP. Entomologists think they control their flashing by regulating how much oxygen goes to their light-producing organs.

Fireflies probably originally evolved the ability to light up as a way to ward off predators, but now they mostly use this ability to find mates. Interestingly, not all fireflies produce light there are several species that are day-flying and apparently rely on the odors of pheromones to find each other.

Each firefly species has its own signaling system. In most North American species, the males fly around at the right height, in the right habitat and at the right time of night for their species, and flash a signal unique to their kind. The females are sitting on the ground or in vegetation, watching for males. When a female sees one making her species’ signal – and doing it well – she flashes back with a species-appropriate flash of her own. Then the two reciprocally signal as the male flies down to her. If everything goes right, they mate.

A good example is Photinus pyralis, a common backyard species often called the Big Dipper. A male flies at dusk about 3 feet off the ground. Every five seconds or so, he makes a one-second flash as he flies in the shape of a “J.” The female Photinus pyralis sits in low vegetation. If she sees a fellow she likes, she waits two seconds before making a half second flash of her own at the third second.

Some species may “call” for many hours a night, while others flash for only 20 minutes or so right at dusk. Firefly light communication can get much more complicated some species have multiple signaling systems, and some might use their light organs for other purposes.

Some Tennessee fireflies put on a synchronized show.

While most male fireflies do their own thing and flash independently of other males of the same species, there are those that synchronize their flashes when there are many others around. In North America, the two most famous species that do this are the Photinus carolinus of the Appalachian Mountains, including in Great Smoky Mountains National Park, and the Photuris frontalis that light up places like Congaree National Park in South Carolina.

In both these species, scientists think the males synchronize so everyone has a chance to look for females, and for females to signal males. These displays are spectacular, and the crush of folks wanting to see them at the most famous locations has made it necessary to conduct a lottery for permission to view them. Both species, however, occur over wide geographic ranges, and it might be possible to see them in other, less congested places.

Apples, Oranges, and Fireflies

The conventional explanation of how a firefly turns its backside into a bioluminescent beacon has always troubled Branchini and other chemists. For starters, it shouldn't work.

Specifically, two of the ingredients mentioned above—oxygen and luciferin—aren't likely to react to each other in the way they would need to in order to produce light.

Understanding why this is gets complicated fast, but a simple explanation is that apples tend to only create chemical reactions with apples, while oranges tend to only create chemical reactions with oranges. In other words, oxygen and luciferin are like apples and oranges.

Branchini's experiments showed the oxygen involved in the firefly's glow comes in a special form called a superoxide anion.

"Superoxide anion is a form of molecular oxygen that contains an extra electron," says Branchini. (Watch video: "The Science of Summer.")

This extra electron gives the oxygen properties of both a metaphorical apple and a metaphorical orange. This means that the molecule would, in fact, be able to cause a chemical reaction with the luciferin like scientists have suspected.

He adds that these superoxide anions could be the way bioluminescence works across nature, from plankton to deep-sea fish.

Understanding how fireflies evolved their glow

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With life's spectacular diversity, it's easy to look at some of its more baroque features and wonder "how could that have possibly evolved?" When researchers look at the actual molecular details, however, there are often rather mundane answers to that question.

One of the latest was provided in a paper released earlier this week by PNAS, which looked at the reason that fireflies are able to glow. The protein that illuminates the bugs, luciferase, turns out to be closely related to one that's normally involved in basic fat metabolism. In the new paper, researchers show that, given the right chemical, the enzyme that's used to make fat can also cause the cells of a fruit fly to glow. Sadly, attempts to feed the chemical to Drosophila failed to make them bioluminescent.

Proteins are made of a long string of subunits called amino acids. Each position in the string can be occupied by any one of 20 different amino acids the precise order in which they appear dictates the protein's structure and function. When two proteins are related by common descent (that is, both are derived from the same ancestral protein), the sequences of the amino acids will be similar—a similarity that's shared with the DNA that encodes the proteins.

So, once researchers cloned the gene for the firefly protein that catalyzes the glow reaction, they were able to determine whether it had any relatives in the genomes of insects. And, not surprisingly, it did: fatty acyl-CoA synthetase. This is an enzyme that plays a key role in fat metabolism, creating an intermediary that allows cells to add more carbons onto growing chains of fatty acids. The firefly protein, called luciferase, catalyzes a very similar reaction, but works with a specialized chemical that produces a lot of light.

So, we know that luciferase didn't get magically poofed into existence. But if you put fatty acyl-CoA synthetase in with the specialized chemical that makes fireflies glow, nothing happens. This raised the question of how the ability to produce light began to be selected for in the first place if there's no light, there's nothing to select.

The authors of the new paper, based at the University of Massachusetts Medical School, reasoned that the process must have started with a mundane, non-glowing fatty acyl-CoA synthetase. If that was identical, then it probably meant that the glow came from a less specialized chemical. So they began testing relatives of the firefly chemical, using the fatty acyl-CoA synthetase from the fruit fly Drosophila. They quickly found a chemical that, when given to Drosophila cells, caused them to emit a dull, red glow. If they put the fly version of fatty acyl-CoA synthetase into human cells, giving them the same chemical would cause them to glow, as well.

Sadly, the one thing that failed was feeding the chemical to living flies. "In principle, the presence of a latent luciferase in fruit flies means that these insects could be rendered bioluminescent if treated with [our chemical] CycLuc2," the authors note. "However, we were unable to detect bioluminescence from fruit flies fed food containing 100 μM CycLuc2."

The results suggest that a random accident—getting the right chemical in cells with a particular enzyme—provided enough glow for evolution to start selecting for it. And, with enough time, both the chemical and the enzyme became specialized, producing a brighter, more intense glow. And, if you've ever seen a night sky filled with fireflies, you'll know it's a pretty spectacular end point for an enzyme that started out making fat.