Romantic fireflies are actually very cruel

The silver candle lights up the cold painting screen in autumn, and the light silk fan flutters against the fireflies.

Because of Du Mu's "Autumn Eve", I have been full of yearning for fireflies since I was a child. But unfortunately, I have lived in the city since I was a child, and I have no way to experience the feeling of being surrounded by fireflies. The few times I encountered fireflies in my life were in my hometown, a remote mountain village. After nightfall, there were no lights in the whole mountain forest, and only the moonlight was left to illuminate the mountain forest. In such a quiet night, a few fireflies would occasionally fly around the small pond behind the house, which looked very romantic.

Although the ancients did not know much about fireflies, they still loved these little insects that flashed dots of fluorescence at night. Throughout the ages, there are not many insects written in literary works. They are either insects with "good qualities" such as spring silkworms and bees, or insects that look romantic and beautiful such as butterflies and fireflies.

But in fact, fireflies only look romantic. When we look deeper into their habits, we will find that fireflies are actually quite ferocious.

Fireflies, as we commonly call them, are actually a type of insect, a large family with nearly 2,000 members. These members are distributed in tropical and subtropical regions around the world, such as East China, South China, and Southwest China. However, the fireflies seen in different regions may not be the same species. After all, there are 200-300 species of fireflies distributed in China.

Fireflies are very picky about their habitats. Wet and decaying grass is their favorite. They are also often seen in moist swamps and wooded areas. Their preference for habitats also led ancient people to mistakenly believe that fireflies were transformed from decaying grass in summer and autumn. The Book of Rites says that "in the last month of summer... decaying grass becomes fireflies." Of course, this is definitely not the case. Fireflies just like to make their homes and lay eggs in decaying grass. When the eggs hatch into larvae, the larvae pupate and become adults, and then the fireflies appear as if by magic.

There are many species of fireflies, and they live in different places. However, the principle of luminescence is exactly the same - in the specialized light organ in the abdomen, the burning energy is transformed into dots of fluorescence. Male fireflies usually have two specialized light organs on the sixth and seventh abdominal segments, while females only have one light organ on the sixth abdominal segment. Most fireflies have the ability to glow from eggs, larvae, pupae to adults, and only a very small number of adult fireflies cannot glow - this type of firefly belongs to the dark light firefly, which can glow in the egg and larval stages, but loses this ability in the adult stage.

The luminescence of fireflies is actually a super-efficient "combustion". There are thousands of luminescent cells in the light organ of fireflies, and the luminescent cells contain luciferin and luciferase. When fireflies breathe, oxygen will enter the luminescent cells and become the "fuel" for luminescence. Under the catalysis of luciferase, luciferin is activated and reacts chemically with oxygen. After oxidation, it enters the excited state and releases bright light. As the energy is exhausted, the luciferin will return to its original state and the fluorescence will disappear. Because the energy utilization efficiency in this process is extremely high, the fluorescence of fireflies is actually very bright, and it is cold light, and no special energy is wasted and converted into heat.

Such changes are repeated in the luminescent cells of fireflies, and fireflies pick up their little lights, lighting up dots of fluorescence at night. Fireflies can not only control the flickering of their own fluorescence, but also control the brightness of their fluorescence by controlling the amount of oxygen entering, so the fluorescence we see is always bright and dark. The various forms of fluorescence also make fluorescence a signal light for fireflies.

The luminescence of fireflies can be used for many functions such as information exchange, trapping, warning, lighting, etc. Especially during the mating season, fluorescence is a signal light for fireflies to court.

Fireflies of the same species communicate with each other through the frequency of their fluorescent flashes. For example, a male firefly will fly low at dusk and flash its fluorescence. If a female takes a fancy to him, she will respond with a special flashing pattern. When the male sees the female's fluorescent flashes, he knows that he has succeeded in holding hands. Because different fireflies have different flashing mechanisms, generally speaking, even if there are several types of fireflies in the same area, everyone can find fireflies of the same frequency and species as themselves.

However, this simple and crude way of courtship also has disadvantages - if there is a "careful firefly" that can imitate the flashing pattern of other fireflies, it is possible to confuse the male firefly and make him go to the wrong place. For example, female fireflies of the genus Photuris will imitate the flashing pattern of female fireflies of the genus Photinus next door to attract male Photinus fireflies.

Hey, why did Yao Saoying do this? Is it because there are not enough males in his own group, so he has to borrow some from the neighboring family?

The answer is obviously not that simple. When the male fireflies happily fly over, what awaits them is not the embrace of the female they like, but the bloody mouth of the female firefly. The male fireflies, who turned into a ghost in the belly in an instant, may never understand until their death how the blind date turned into a killer.

In fact, the demon fireflies do this to pass on their lineage. Male fireflies have a special toxin in their bodies. When they are attacked by natural enemies, they will immediately secrete this venom. Even if they have been eaten by natural enemies, this venom will make the natural enemies spit them out unwillingly. By eating male fireflies, female demon fireflies can absorb their toxins and use them for themselves. Not only that, they can also pass this powerful defense method to their offspring, so that their offspring can also have this self-protection ability to drive away natural enemies.

The demon firefly can not only imitate the flashing pattern of the firefly, but also imitate other fireflies such as Lampyrinae and Pyractomena. In general, among a group of honest fireflies, the deceptive demon firefly is simply invincible.

Although they have lost their ability to imitate, other fireflies are still quite fierce—of course, to their prey. Firefly larvae are carnivorous, and small snails, slugs, earthworms, and even shells near the water are all big meals for firefly larvae. For example, the prey of female firefly larvae is millipedes that seem to have no idea where to bite. The small female firefly can bite millipedes that are several times larger than it, and after a fierce fight, it will happily eat until its belly is full.

The article is produced by Science Popularization China-Starry Sky Project (Creation and Cultivation). Please indicate the source when reprinting.

Author: Hydra Science Author

Reviewer: Yin Haisheng, Senior Engineer, Researcher-level, Shanghai Insect Museum, Chinese Academy of Sciences