What kind of insect is the "katydid" in "The Book of Songs"?

Produced by: Science Popularization China

Author: Li Bo (Shaanxi Institute of Biological Agriculture)

Producer: China Science Expo

In China, there are four major events in life: weddings, funerals, and marriages. This shows how much the Chinese value marriage. Nowadays, weddings, whether Chinese or Western, are always accompanied by a banquet for relatives and friends. But did you know that in the Western Zhou Dynasty 3,000 years ago, if you wanted to attend someone else's wedding, you had to learn to sing a poem first:

The wings of the locust are so beautiful. May your descendants be vigorous.

The wings of the locusts are rustling. May your descendants be numerous.

The wings of the locusts are bowing. It is good for your descendants to be awake.

——The Book of Songs·Zhou Nan·Cicada

From the phrase "Yi Er Zi Sun", we can see that this is a poem wishing the newlyweds many children and grandchildren. The whole poem repeatedly mentions an insect - "katydid" in a repetitive rhythm. So, what exactly is a katydid? Today, I will introduce it to you.

A respected fertility expert

Among insects, katydids are relatively large, usually about 40-60mm in length, with a grass green or gray body color. The antennae of katydids are thin and long, and they have a pair of large and bright oval compound eyes (composed of many small eyes) located on both sides of the front upper part of the head. There is a well-developed mouthpart under the head, which is particularly good at chewing plant tissue. There are three pairs of legs on its chest, the front two pairs are suitable for crawling, and the muscles of the back pair are more developed, mainly used for jumping. The wings of katydids are also unique, usually the left wing covers the upper side of the right wing, and the hind wings are slightly longer than the front wings.

The appearance of katydids is very similar to another insect we know, the locust. In the "Poetry Anthology" written by Zhu Xi in the Song Dynasty, there is such a description: "Katydids belong to the locust family. They are tall and green, with long horns and long legs. They can make sounds by touching their legs together. They give birth to ninety-nine offspring in their lifetime..."

A

B

Figure 1 A. Chinese Katydid B. Green-striped Grasshopper

(Photo sources: Picture A provided by Mao Shaoli, Picture B provided by Tan Jizhao)

The so-called "ninety-nine children" is not an accurate number, but describes its strong reproductive capacity. It is precisely because of its strong reproductive capacity that locusts cause extremely serious damage to agricultural production.

Figure 2 Severe locust plague

(Photo source: veer photo gallery)

Although the ancients were afraid of locusts, they also envied their strong fertility. Because science was not yet developed, productivity was very backward, and people were the most important labor force, so reproduction was regarded as the most important and sacred mission.

Katydids not only look similar to locusts, but also have similar reproductive abilities. Therefore, in those days when productivity was extremely underdeveloped, in order to better adapt to nature and survive in the harsh environment, our ancestors placed their beautiful wishes of having many children and grandchildren and endless life on this inconspicuous insect.

A wide variety of cute insects

At present, there are roughly 930 genera and 6,100 species of katydids known in the world, which are distributed all over the world, but most of them are distributed in tropical and subtropical regions.

Katydids mainly live in forests and grasslands, and a few species live in burrows, tree holes, and rock crevices. The diversity of their living environments has also created a rich diversity of katydid species, making them the "ever-changing giants" of the insect world.

For example, the lichen katydids distributed in South America are good at "transformation" and have excellent mimicry skills (Figure A below); the giant sand katydids distributed in New Zealand can be called the giant in the katydid world (Figure B below); the blue bull katydids distributed in South America are "brave and good at fighting", like a brave fighter (Figure C below); the red-eyed devil katydids distributed in the United States and Mexico can even prey on small lizards, frogs and even birds (Figure D below).

Figure 3 Different types of katydids

(Photo source: "Ren Dai Shou Hu" photography competition)

In China, there are about 110 genera and 450 species of katydids found so far, the more common ones are katydid, Katydid, and Weaver. Among them, the most popular among Chinese people are the katydid and Weaver, which we usually call "katydid" and "weaver".

Figure 4: Kabuto

(Photo source: provided by Mao Shaoli)

The singing master whose voice never stops

Vocal communication is one of the most important ways of communication for animals, and is often used in courtship, mating, hunting, and avoiding predators. Studies have found that Orthoptera insects are the most diverse singing creatures today, including common crickets, katydids, locusts, etc.

Only male Orthoptera insects can make sounds, but different members of the order Orthoptera make sounds in different ways. They can be roughly divided into two categories: katydids and crickets make sounds by rubbing their front wings against each other, while locusts make sounds by rubbing their hind legs against their front wings (or hind wings). Therefore, Master Zhu's description of katydids being able to make sounds by "two legs touching each other" is inaccurate. He confused katydids with locusts.

A large amount of fossil evidence shows that katydids flourished in the Mesozoic Era, and therefore are considered by scientists to be ideal subjects for studying the acoustic evolution of animals. The latest results published by the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences in the Proceedings of the National Academy of Sciences (PNAS) in December 2022 are based on Mesozoic katydid fossils. By analyzing the morphological characteristics of katydid sound organs, the researchers revealed the evolution of the acoustic behavior of Mesozoic katydids, providing strong evidence for the hypothesis of acoustic co-evolution of insects and early mammals.

During the long evolutionary process, different species of katydids have formed obvious differences in the volume, frequency, and pitch of their calls. In this way, female katydids are only attracted to the calls of male katydids of the same species, thus maintaining reproductive isolation between different species. Just like what we usually say, although we are related, we cannot communicate many important things because we do not speak the same language...

However, if you want to truly "sing loudly" in a noisy natural environment without being disturbed by the outside world, the key lies in whether your own musical instrument and playing skills are powerful.

Through electron microscope observation, you will find that the male katydids have a row of serrated structures like those on a file on their forewings - "sound files". Due to the obvious inter-species differences in sound files and the different frequencies of friction between the forewings, the singing ability of male katydids has been greatly improved, making them well-deserved "singing masters" in nature.

Figure 5 The vocal teeth of the male Rhombus punctatus (A, B) and the male Rhombus punctatus (C, D) at different magnifications

(Image source: Reference 7)

In addition to singing ability, katydids' powerful vocalization ability is also closely related to reproduction.

Unlike mammals, female katydids have a pair of "ears" on their front legs, which scientists call "hearing organs." The chirping of male insects of the same species can stimulate the periosteum on the hearing organ to produce a unique vibration frequency even thousands of meters away, thereby awakening the female insect's instinct to reproduce.

Figure 6 The auditory organ on the front legs of a Jurassic katydid fossil can be clearly seen (te)

(Image source: Reference 8)

Resourceful Survival Expert

The reason why the katydid family can spread and evolve around the world is closely related to its strong ability to adapt to the environment. After more than 200 million years of evolution, they have become resourceful survival experts.

The katydids we usually see are usually green or gray, which is a protective color for them to adapt to the forest and grassland environment. They can blend well with the background of the environment and are not easily discovered by natural enemies. The lichen katydids mentioned above are masters at hiding themselves through mimicry.

In addition, as omnivorous insects, they are good at eating anything. Some carnivorous species have even developed good skills in order to get enough food. For example, the ghost king katydid, which has spikes all over its body and a sharp mouth and large jaws, not only looks ferocious, but also has a bad personality. They are so cruel that they dare to kill geckos, mantises, and even small lizards, which are usually insect killers, and eat them quickly. They really deserve their reputation.

Figure 7 Katydids have good camouflage. If you don’t look carefully, you may find it difficult to spot them in the grass.

(Photo source: provided by Tan Jizhao)

Conclusion

Every hot summer day, I always think of the emerald green katydids in the bamboo cage on the wall of my childhood yard. With the bright moon and the fresh breeze, listening to the insects singing in my ears, it seems that the night is full of poetry.

Nowadays, with the high-rise buildings in the city, it is hard to find the traces of katydids in this jungle of steel and concrete. Even in the countryside, the fun of children playing with insects is being replaced by various electronic products. And the wedding blessings given to newlyweds are no longer the "Katydid" in the Book of Songs, but have become the size and thickness of the red envelopes.

Since when, nature seems to be getting farther and farther away from us...

Acknowledgements:

We would like to thank Dr. Mao Shaoli from Xi'an Botanical Garden of Shaanxi Province and insect expert Mr. Tan Jizhao and other friends for providing a large number of precious photos and valuable suggestions for writing this article.

References:

【1】Zhu Xi. Poetry Collection. Zhonghua Book Company[M], 1958.

【2】Lu Ji. Mao Shi: Plants, Birds, Beasts, Insects and Fishes[M]. Zhonghua Book Company, 1985.

【3】Wang Lei. Insect Culture in the Book of Songs. Journal of Qingdao Agricultural University (Social Science Edition)[J], 2016, 28(03):87-89

【4】 Shen Junxian. Sound-taxis and positioning accuracy of katydids. Acta Biophysica Sinica[J], 1989, 2(03): 252-256

【5】 Shen Junxian. The influence of the katydid vocal tract system on directional hearing. Science Bulletin [J], 1990, 1584-1586

【6】Liu Fei. Taxonomic study of some species of the subfamily Katydidinae in China: evidence based on sound and morphology[D]. Shihezi University, 2020

【7】Wang Jing. Study on some of the sounds and vocal teeth of katydids. Shanxi Normal University[D], 2014.

【8】Xu Chunpeng et al. High acoustic diversity and behavioral complexity of katydids in the Mesozoic soundscape[J]. PNAS, 2020.119(51):1-8