Hibernating underground for dozens of months, it amazed me the whole summer when it opened

Nothing heralds the arrival of summer better than the chirping of cicadas. These insects lying on tree trunks chirp tirelessly, becoming the most enthusiastic singers of summer.

Image source: emily stone

According to the ancient saying: "When cicadas begin to sing, summer begins to bloom." This means that after the summer solstice, mature nymphs that have been dormant underground break out of the soil and begin to emerge.

After that, the male cicadas will have to rely on their loud voices to attract female cicadas in just one summer, thereby fulfilling their mission of passing on their genes.

After mating, the female cicada lays hundreds of eggs in the cracks of grass stems or tree bark.

Female cicada laying eggs. Image source: BBC Earth

Over the next few weeks, the flea-like larvae (nymphs) hatch and drop toward the ground, burrowing into the soil.

They will live here for the next year or even several years, feeding on the sap of underground tree roots, preparing for their next appearance under the sky.

No.01

Why are cicadas so loud?

Imagine if you had been gnawing on tree roots in the dark underground for several years, but only had a few weeks to find a girlfriend, mate and reproduce in the sun, and there were even thousands of competitors around you. Faced with such an urgent arms race, each male cicada could only scream desperately to win the favor of female cicadas.

Image source: BBC earth

Unlike most insects, cicadas have a unique sound-producing structure.

Generally, we think of "noisy" insects including crickets, katydids, and katydids, most of which produce noise by rubbing two parts of their bodies together.

Image source: LNZYX/ISTOCK/THINKSTOCK

But cicadas are different. The most common structure they use to make sounds is the tympanic organ. Every male cicada has a pair on the back and sides of the first abdominal segment, which are mainly composed of rib-like membranes at the bottom of the abdomen and attached muscles.

When the eardrum is pulled by the muscles attached to it, it causes the bones on both sides of the body to bend. The muscles relax and then rebound, and in this ups and downs, a loud sound is produced.

Image source: wired

The frequency of eardrum muscle contraction can reach 120 to 480 times per second, which is enough for the human ear to feel the endless waves of vocal music.

The male cicada also has a hollow, balloon-shaped abdomen that amplifies the sound emitted from the eardrum, and as the resonant frequency of the abdominal air sac matches that of the eardrum, we can hear the sound gradually getting louder.

Image source: wired

Sometimes, to further amplify the sounds they make, male cicadas will sing together in chorus, creating an unparalleled orchestral piece dedicated to all the female cicadas in the world.

In addition, some cicadas can also wave their wings to direct the sound in different directions, allowing female cicadas to experience 360-degree surround sound. It is no exaggeration to say that the body of a cicada is no less than a natural musical instrument, and the performers are themselves.

No.02

How do “dumb” cicadas make sounds?

Among the more than 3,000 species of cicadas in the world, the vast majority use tympanic membranes to make sounds, which is the most effective vocal organ evolved by the Cicadoidea superfamily.

There are also relatively few cicadas whose vocal organs are similar to those of insects such as crickets, using the trailing edge of the forewing and the leading edge of the hind wing with pronunciation teeth to rub against each other to produce sound.

The chirping behavior, chirping type, frequency and time domain characteristics make it easy to distinguish the species of cicadas, especially the closely related species of the same genus. For example, the chirping rhythms of two mountain cicadas that are difficult to distinguish in morphology are obviously different; the green grass cicada and the blue grass cicada that look like twins also have great differences in their chirping.

Therefore, the chirping of different cicadas sounds different to cicadas, which makes the chirping of cicadas an effective way to isolate one population from another - the acoustic isolation mechanism .

Image source: yabai

However, it is worth noting that cicadas (Cicadidae, Cicadettinae) under the genus Karenia celatata have neither eardrums nor organs that can be rubbed to make sounds, so they are also considered "dumb" cicadas. So how do they call to their own kind?

A "dumb" cicada Photo credit: Christian

Entomologist Christian Nansen from the University of California, Davis, and Professor Wei Cong from the College of Plant Protection at Northwest Agriculture and Forestry University answered this question in their research.

"While cicadas in the genus Karenia lack the tympanic sound-producing structures characteristic of most other cicadas, the term 'dumb' is misleading because they do make sounds," said Nansen.

The researchers used high-spectral resolution imaging technology to photograph the structures involved in the sound production of the "dumb" cicada, including the forewings, gill covers, cross-shaped ridges on the body surface, and the roots of the wings, and found that they all underwent morphological changes.

In other words, "dumb" cicadas can produce sound by hitting the gill cover with the ribs of the front wings, which is more like beating a drum than sounding by compression and friction of the eardrum.

Pay attention to the wings. Source: Research Attachment

If its sound is added to the cicadas' singing, it would be like forming a symphony orchestra with diverse styles and loud voices. At the same time, this new percussion sound-making mechanism is also used for intra-species communication among the Karenia cicadas and can also play the role of singing.

In addition, the researchers observed that when the first male in the group starts flapping its wings to make a sound, more and more males around will join in, forming a chorus. Even the sound of clapping or tapping bamboo sticks can trigger the chorus of cicadas.

References:

1. Lei Zhongren, Zhou Yao. Characteristics of cicada chirping and their taxonomic significance: Homoptera: Cicadoidea[J]. Acta Entomologica Sinica, 1994, 16(1):51-59. DOI:10.1007/BF02943514.

2.Why are cicadas so noisy?

https://www.britannica.com/story/why-are-cicadas-so-noisy

3.How Do “Mute” Cicadas Produce Their Calling Songs?

https://journals.plos.org/plosone/article? id=10.1371/journal.pone.0118554

END

Author: Fish

Winner of the Silver Award for Outstanding Science Popularization Works of China Science Writers Association

For those who love steamed fish head, spicy fish head and other fish head