Fun Fact - Fireflies

Despite its name, a firefly is not a fly, but rather a beetle with wings. There are about 2,000 species of fireflies, contributing to the 400,000 species of beetles that constitute nearly a quarter of all animal species on Earth. biologists often remark that if a Creator fashioned each animal "according to its kind", as suggested by Genesis 1:24, then he has an inordinate fondness for beetles.

A firefly generates flashes of light through a process called bioluminescence, primarily to attract a mate. Why then doesn't the firefly get eaten? Whenever an animal advertises itself, through bright colors or flashing lights or other signals, it is often poisonous or harmful in some fashion. The signal doesn't mean, "Hey, come over here and eat me", that wouldn't make evolutionary sense. It usually means, "Stay away from me, I'm dangerous, or at least not worth your time." This is illustrated by the stripes on a skunk, or the bright colors on the poison dart frogs of Central and South America. As it turns out, many species of firefly contain steroid poisons similar to these frogs. They can flash away without being eaten because they taste bad, and if enough fireflies are ingested the predator could become ill.

Even larvae can emit light, and these are sometimes called glowworms. In 1902, Paul Lincke wrote an operetta, Lysistrata, that contained the song Glow-Worm. Johnny Mercer modified the lyrics for a 1952 recording by the Mills Brothers, which spent 21 weeks on the charts, including 3 weeks at number 1. In the 1950's everyone knew the song Glow-Worm. I'm almost old enough to remember it. It is all but forgotten now, and such a song, if released today, almost certainly would not reach number 1. Times change. Here are the lyrics.

Shine little glow-worm, glimmer, glimmer
Shine little glow-worm, glimmer, glimmer
Lead us lest too far we wander
Love's sweet voice is callin' yonder
Shine little glow-worm, glimmer, glimmer
Hey, there don't get dimmer, dimmer
Light the path below, above
And lead us on to love

Glow little glow-worm, fly of fire
Glow like an incandescent wire
Glow for the female of the species
Turn on the AC and the DC
This night could use a little brightnin'
Light up you little ol' bug of lightnin'
When you gotta glow, you gotta glow
Glow little glow-worm, glow

Glow little glow-worm, glow and glimmer
Swim through the sea of night, little swimmer
Thou aeronautical boll weevil
Illuminate yon woods primeval
See how the shadows deep and darken
You and your chick should get to sparkin'
I got a gal that I love so
Glow little glow-worm, glow

Glow little glow-worm, turn the key on
You are equipped with taillight neon
You got a cute vest-pocket *Mazda*
Which you can make both slow and faster
I don't know who you took the shine to
Or who you're out to make a sign to
I got a gal that I love so
Glow little glow-worm, glow
Glow little glow-worm, glow
Glow little glow-worm, glow
Glow little glow-worm, glow

Special organs on the abdomen generate light using energy stored in adenosine triphosphate (ATP) and special proteins and enzymes in the presence of oxygen. The resulting light is green, yellow, or pale red, with virtually no infrared or ultraviolet wave lengths. all the electromagnetic energy is in the visible spectrum. This is called "cold light", with no waste heat, and it is the goal of human engineers. Let's compare the efficiency of nature and technology.

A candle has a luminous efficacy of 0.04%. Almost all the chemical energy of the wax is converted into heat. A Coleman lantern is a step up at 0.3%. The simplest tungsten light bulb reaches 2%, but now we have to take into account the process of generating and distributing electricity, which can deliver as little as 30% of the fossil fuel's energy to your home. Let's set that aside for the moment and assume electricity is magically available at the wall socket. Now the incandescent light bulb shines at 2 to 8 percent. The compact fluorescent bulb achieves 12%, as does a commercial LED (light emitting diode) lamp, though some LEDs can reach 20%. A low pressure sodium lamp seems to hold the top spot at 29%. In contrast, the cold light generated by a firefly constitutes nearly 100% of the chemical energy that creates it. The only significant losses are absorption and internal reflection as the light passes through the insect's transparent cuticle to the outside world. Such losses are difficult to measure, but if even half the light escapes, a conservative estimate, the result is still better than anything we can produce in the lab. In fact the firefly's transparent cuticle has been optimised by evolution for high transmittance, and engineers are keen to copy this design. A fragmented transparent surface, inspired by the firefly, applied to an LED, could improve its overall efficiency by 55%.

Further Reading

Firefly, a family of beetle
Poison dart frogs and their bright colors
The Glow-worm song performed by the Mills Brothers
Bioluminescence, how it works
Light efficiency and power plant efficiency
Fireflies and LEDs