Fireflies are what make summer nights special. They usually hide in the grass and emit a mystical green light, hoping to attract the attention of the opposite sex. And they do it beautifully. Have you ever seen flickering trees, as if they were wrapped in an electric garland? As always, behind the romance lies a complex chemical reaction.
How fireflies glow?
It is due to a unique organ in their body – the photophore. It is located in the tail of the abdomen and has a complex structure consisting of three functional layers. For illustration, imagine an ordinary flashlight: the bottom layer is reflective and should reflect the light produced by the complex chemical reaction of the middle layer. The tissues of the middle layer consist of photocells – cells capable of converting oxygen into light. The upper functional layer is represented by a transparent light-transmitting cuticle.
A large amount of oxygen is displaced from the cellular mitochondria to create the glow of a firefly by being replaced by nitric oxide. Insects do not have lungs, so all the necessary processes for their survival occur within their cells, including respiration. The nervous system regulates the “flashlight” modes.
There are plenty of organisms in nature that “carry light” – coral reefs, deep-sea fish, mollusks, jellyfish, etc. Both fireflies and these organisms use the pigment luciferin to produce their glow, which is activated by luciferase with the help of adenosine triphosphate (ATP), the universal unit of cellular energy, and when oxidized, it creates the magical glow. This occurs during the separation of carbon dioxide molecules when luciferin molecules exit their excited state, releasing light energy, causing the firefly to glow in the dark.
The mysterious and cool glow of fireflies doesn’t actually produce any heat, except maybe to the soul. There are no infrared or ultraviolet rays in photons. But about 98% of the expended energy is used for illumination, unlike an ordinary electric light bulb, whose efficiency is only 10%, and whose energy is partly wasted on useless heat.
Why Fireflies Glow?
Why do fireflies light up, what is the purpose of this? The thing is, bioluminescence can and should be attributed to a way of communicating with mates – a very romantic and beautiful one. For example, males of North American and tropical species organize a real pre-wedding flash mob. The insects sit on a tree and, at dusk, flicker randomly. Over time, they catch a single rhythm, synchronizing into a single lighting device – and the tree seems decorated with a living garland.
By the way, female fireflies are not particularly beautiful – unlike males, they do not have wings, but they also luminesce synchronously in response to the boys from the tree. However, females are cunning – especially the Photuris species, which pretend to be a different species – Photinus. Later, the deceived Photinus males end up being eaten, while the females gain confidence in tomorrow, because the bodies of their prey contain a special enzyme that repels birds and spiders. Sometimes cannibalism occurs without any apparent reason.
Female fireflies emit a special signal indicating that they are ready to mate, allowing males to know where to fly. Generally, the brighter a male shines, the more female attention he attracts.
In addition, their larvae, pupae, and eggs also glow, which scientists cannot explain. However, it can be assumed that this is a way for them to signal to predators that they are inedible.
The most common species in Eurasia is called the “Ivanov worm”. It is believed that these insects become active specifically on the night of Ivan Kupala.
Interestingly, out of 2,000 species, only a few fireflies actually light up, while the rest primarily function during the day.
What could fireflies teach us?
Besides instilling a sense of beauty in people, fireflies can boast about the efficiency of converting their energy into light. Recently, researchers studying the surface of fireflies’ bodies noted their scale-like structure resembling roof tiles. Using nanotechnology, they attempted to create a similar structure on the surface of an LED, which increased its efficiency by 55%!
According to the beliefs of some people, fireflies are the souls of the dead who cannot find their way. And how else to explain this magic? In the philosophy of feng shui, the firefly is positioned as a symbol of the rebirth of souls. The extraordinary glow of the insect gives it an almost sacred character.
However, the Japanese endow fireflies with the greatest number of traditions and deepest symbolism. As befits a warm and humid climate, they shine with much more enthusiasm than their pale relatives from middle latitudes. Therefore, their mating period is a grandiose light show. In Japan, even the Firefly Festival – Hotaru Matsuri is celebrated.
People have used fireflies for a variety of purposes – as hair ornaments, as tools for creating a romantic atmosphere, as lighting devices, and as assistants in the fight against evil spirits. Nowadays, synthetic luciferase, originally extracted from living insects, is used in forensic medicine as well as for monitoring the quality of food products.
The firefly population has sharply declined, and this is due to pollution and the destruction of their habitats. The problem is that they do not migrate from these areas, they simply disappear.