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This article comes from the official account of Wechat: SF Chinese (ID:kexuejiaodian), author: SF

(photo Source: Pexels) since ancient times, the plague of locusts has been the main disaster affecting production and life in China, second only to floods and droughts, and is known as the third largest disaster in China. Locusts can be seen everywhere from the south of the Great Wall to the north of the Yangtze River, to the sea in the east and to the Guanzhong Plain in the west. Locusts occurred every three years on average from the pre-Qin Dynasty to the beginning of the 20th century, and almost every year from the beginning of the 20th century to the founding of New China. When the plague of locusts is serious, swarms of locusts block out the sun, and the place where they pass is barren and thousands of miles away.

(by Mei Lin / tr. by Robert Taylor)

It can be seen that swarms of locusts pass by, and everything around them can be eaten by them, including themselves. This is not a joke. Locusts do eat each other of the same kind.

Why do animals eat their own kind? Cannibalism is a very common phenomenon in the animal kingdom. This phenomenon is an adaptive behavior for animals to deal with survival crisis and ensure the continuation of the population.

When it comes to mating, the female eats the male, and maybe the first thing we think of is the mantis. For example, in the picture of the thin-winged mantis, the male and female engage in a "wrestling match" before mating. If the male wins, he can mate smoothly; if he loses, he may be eaten by the female after mating. Some animals eat each other in order to complete reproduction. For example, when some spiders mate, the male will take the initiative to come to the door and let the female eat it and become the energy for the female to reproduce. Most cannibalism in the animal kingdom is caused by "not having enough to eat"-when food is scarce, the same species will compete fiercely and even eat the same species for their own survival. In this way, it can not only reduce the competition for limited food, but also make up for the lack of energy caused by the lack of food. For example, some seemingly docile birds fight a life-and-death battle between chicks when food is scarce, and only one or two of the largest and healthiest chicks survive.

Similarly, cannibalism of locusts is also an adaptation beneficial to their survival. Recently, scientists have found that cannibalism plays a role in driving locust swarms to fly. "in fact, locusts eat each other from behind," said Bill S. Hansson, an evolutionary neurobehaviorist at the Max Planck Institute for Chemical Ecology in Germany. "for their own safety, locusts must move, or the guys behind will eat it."

In spite of this, for locusts, a large group of "travel" is still particularly dangerous-who can rest assured to be followed by a gluttonous companion. So how do locusts make sure their companions don't eat themselves?

Locust: I warn you, it's dangerous to eat me! To study the mechanism by which locusts prevent themselves from being eaten by their own kind, Hansen and his colleagues carried out research. They put 250 locust larvae in the same cage to mimic locusts that had just begun to swarm. Then, using gas chromatography, locusts emit odorous compounds in these crowded cages. Because researchers believe that locusts in locusts may use odors to keep their own kind from eating them.

Among these compounds, the researchers paid special attention to phenylacetonitrile. Phenylacetonitrile can be converted into toxic cyanide, thus preventing predators such as birds from catching locusts. So does this compound have the same effect on other locusts?

The molecular formula of phenylacetonitrile. This compound can not only be converted into toxic cyanide, but also the intermediate products of some sedatives, sleeping pills, stimulants and other neurodrugs, which are listed as prohibited drugs in some countries and regions. To test the hypothesis, the researchers used gene editing techniques to breed two species of locusts: one related to the deletion of genes that produce phenylacetonitrile, locusts can not produce phenylacetonitrile, these locusts become the target of their companions to hunt; another gene related to the production of phenylacetonitrile receptor has been knocked out, which means these locusts do not smell phenylacetonitrile, they unscrupulously prey on the same species.

Based on these results, the researchers believe that phenylacetonitrile may be the chemical pheromone that locusts prevent locusts from eating themselves. Other locusts in the colony smell phenylacetonitrile and no longer prey on the same species.

Why should we know "how locusts are not eaten by their own kind"? Seeing this, some friends may ask, "what's the use of scientists studying this? why do we need to know how locusts are not eaten by their own kind?"

Gregory Sword, an entomologist at Texas A & M University in the United States, said, "since blocking locusts from producing or sensing pheromones, locusts can kill each other. It is possible to use the cannibalism of locusts to self-regulate the population and reduce the number of individuals in the locust swarm. In addition, pheromones such as phenylacetonitrile may have a similar effect on predators, after all, phenylacetonitrile is supposed to protect against predators. If locusts cannot produce these pheromones, they will be more vulnerable to predators. This method of biological pest control is both effective and environmentally friendly.

References:

The chemical ecology of locust cannibalism | Science

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