How do locusts find mates? Scientists have figured it out

Produced by: Science Popularization China

Author: Insect Intern (PhD in Biology)

Producer: China Science Expo

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Speaking of locusts, today's children may be a little unfamiliar with them. Their memories are only of the grasshoppers they caught in the grass when they were young and on the dining tables in some places.

However, in the early years, when our parents and grandparents lived, people were terrified by the word "locust". This can be seen from the creation of characters. The word "locust" is a combination of "insect" and "emperor". The ancients were helpless in the face of the overwhelming locust plague. They believed that locusts were the emperor of insects and even built locust temples to worship them and pray that there would be no locust plague. Therefore, locust plagues, along with floods and droughts, became the three major disasters of ancient Chinese agricultural civilization.

locust

(Photo source: veer photo gallery)

Our ancient ancestors fought against locusts for thousands of years, but it was not until the founding of New China that locust plagues were eliminated through scientific prevention and control. Even so, the threat of locusts throughout the world cannot be underestimated. Almost every year we can see from the news that locusts bring serious disasters to different parts of the world.

Therefore, in order to prevent problems before they occur, our country has been conducting research on locust control, and has long gone beyond statistical classification and morphological observation, but has gone deep into the molecular field and even is at the forefront of the world.

Solitary locusts and gregarious locusts

In a recent study, Chinese scientists discovered that solitary female locusts release large amounts of dibutyl phthalate (DBP) to attract solitary and gregarious males, allowing them to reproduce successfully.

The so-called solitary locusts are actually relative to the gregarious locusts. Solitary locusts are actually the green grasshoppers jumping in the summer and autumn grasslands, because migratory locusts exist in a scattered form in nature. Only when some external factors make them gather will they change into a gregarious state. The solitary migratory locusts are green all over, blending into the grass, living quietly in the wild. Only when they want to reproduce, a male and a female locust will come together. After completing their mission, they will separate and continue to be "lone rangers."

The gregarious locusts are completely the opposite. The bodies of their young are mainly brown and black, which makes them look out of place in the grass. A large group of locusts live together and continue to grow like a snowball. They rarely act alone, eventually forming a locust plague.

Solitary and gregarious locusts

(Photo source: Voice of Chinese Academy of Sciences)

So gregarious and solitary locusts are relative terms, and the two forms can transform into each other. Scientists have previously discovered the important compound 4VA transformed by these two locusts, as well as the principle of the color change of these two locusts. Interested friends can read our other popular science articles.

Locust swarm

(Photo source: veer photo gallery)

In gregarious locusts, since they form a huge group with a male-female ratio of about 1:1, it is easy to get rid of singles. But what about solitary locusts? Each of them is a "lone ranger", and some have never seen their own kind since childhood. So can they still reproduce successfully? But even so, scientists have found that solitary locusts can still reproduce and produce offspring. What is the reason?

Locust breeding

Many insects can make sounds, and locusts are no exception. So could it be that the sound attracts locusts of the opposite sex? However, scientists' current research has not found evidence that sound plays a role in attracting locusts of the opposite sex.

Prior to this, the sex pheromone of the desert locust (Schistocerca gregaria) has also received attention. And it has been found that compounds released by female desert locusts, such as 2,6-nonadiene and valeric acid, can trigger electrophysiological responses (EAGs) in males and induce mating behavior. Benzyl acetonitrile (PAN), which was previously believed to be the aggregation pheromone or sex pheromone of desert locusts, was proved to be a warning compound some time ago and is the precursor of the toxin used by migratory locusts (Locusta migratoria) to fight bird predation and cannibalism.

This suggests that the differences between gregarious and solitary locusts are not only visible, but also odorous. For example, 4-vinylanisole (4VA) released by gregarious locusts acts as an aggregation pheromone, attracting individuals of the same species to form groups and promoting the synchronous sexual maturation of female locusts. So scientists naturally wondered whether solitary locusts would have a similar compound to attract their own species? After all, smells can travel far.

Locust larvae

(Photo source: veer photo gallery)

First, scientists have discovered that some structures responsible for smell on the antennae of locusts are different between males and females, and are more numerous in adult locusts, which further confirms the hypothesis of odor information: there should be a special chemical signal to achieve communication between male and female locusts.

So scientists collected all the volatile compounds from male and female locusts, separated them one by one, and conducted locust behavior experiments. After unremitting efforts, they finally found that dibutyl phthalate (DBP) released in large quantities by solitary female locusts can attract solitary and gregarious male locusts, and the fewer the locusts, the stronger the attraction. Isn't this a perfect solution to the love problem of solitary locusts! This allows solitary locusts with extremely low density to successfully find partners and reproduce.

So, what is the significance of this phenomenon we discovered, in addition to understanding the "love" journey of solitary locusts? The answer is yes. First of all, biology is a basic science that requires extensive research accumulation. Sometimes a study on insects may provide ideas for certain future human research. Of course, this is a certain amount of luck. On the other hand, because locusts can transform between gregarious and solitary, this attractant, which is mainly produced by solitary female insects, is also a potential stock for detecting and preventing locust plagues!

References:

[1] Cui W, Ge J, Chen D, Nie