Exquisite butterfly (golden butterfly on the left, beautiful butterfly on the top right, citrus butterfly on the lower right)
Butterflies (Papilionidae) is a more beautiful class of insects, they are larger, colorful, graceful, unique markings make them fly in the air is particularly eye-catching, is a more popular type of butterfly. According to statistics, there are more than 550 species of butterflies in the world, and their traces are almost all over the world. For example, the beautiful butterflies depicted in the famous Chinese Liang Zhuzhong, the citrus butterflies commonly found in the orange groves, and the golden butterflies in Xishuangbanna in summer, as well as many large butterflies that are often used for specimens in the market, are mostly phoenix butterflies.
Why are butterflies so beautiful? And dare to dance in such a treacherous jungle life? How did its life come to be? This is due to the unique survival strategies of the butterfly's superb use of poison, especially in the larval stage. Today we will talk about the "poisonous tricks" of the butterfly and the secret behind it.
No 1. Gather the poison of food in the body to warn the enemy
The magnificence of the butterfly lies in the adult, but the survival lies in the larval stage. The larval stage is relatively fragile due to its long duration and weak crawling ability. Although the butterfly larvae are also called "caterpillars", most of them are smooth and hairless guys, which is not consistent with the appearance of the "caterpillars" in our minds, and the butterfly larvae do not rely on poisonous hair to protect themselves, but have other tricks.
The larvae of the butterfly are very unique in feeding habits, and their hosts are mostly plants of the family Rubiaceae, Aristolochiaceae, Lauraceae and Umbellifera, such as citrus butterfly larvae like to eat oranges and pepper leaves, golden butterflies like to eat fennel, golden butterflies like to eat aristolochia and so on. Through these unique foods, the larvae acquire strange tastes or toxins to enhance their defenses against predators.
Some of the more "arrogant" caterpillars with strong toxins have also abandoned their implicit lifestyles because they have obtained super-strong shelter poisons from food. Instead of hiding, they blatantly eat on the surface of the leaves, "warning" their opponents, saying, "Old capital is poisonous, you better not provoke old capital!" "Scientifically called aposematism, such as the type of butterfly that feeds on aristolochia bells, is one of these players.
For example, The larva Papilio noblei of Banna' natal butterfly, which lives in groups on the front of the leaves, looks quite terrifying (Photo by Liu Jingxin)
No 2. Mimetic small snake, head spit snake letter
Another famous feature of butterfly larvae is mimesis or camouflage, which can be disguised as a "snake" or camouflage as "guano", such as the citrus butterfly, which when it was born, looked like bird droppings. As it grows up, it not only has snake-like false eyes, but also a pair of glands around its neck, and when it encounters danger, it suddenly rises up, spews out "snake letters", and releases a strange smell to intimidate its opponents.
Butterfly Papilio lowis larvae mimetic bird droppings as children (Pinterest image)
Citrus butterfly larvae will squeeze out glands when they encounter danger, much like a snake spitting out a letter (image from the Internet)
No 3. Variable insect body, changeable strategy
In addition to poisonous, stinky, prosthetic eyes, and spitting snakes, the larvae of the butterfly also have a variety of self-preservation strategies. Take, for example, the most common citrus butterfly on orange or pepper trees.
The first four stages of the first four stages of birth, the body color is black, yellow and white, the form is like bird droppings, by simulating bird droppings and reducing the attack of natural enemies such as birds; after five years of age, as the body grows and the hormones in the body decrease, the larvae body color gradually changes to green, hiding itself (crypsis) in the green leaves, becoming a hidden mountain forest. Once they encounter an enemy, they will show their weapons, pretend to be small snakes, and spit out poisonous gas to scare off their opponents. It can be described as a fickle master of nature.
Larval morphology of citrus butterfly by age: A. A first-instar larvae that have just hatched to feed on egg shells; Second-instar larvae sticking out of the stinky horn; Third-instar larvae;D. Fourth-instar larvae; Five-year-old larvae sticking out of the stink horn;F, G. fifth-instar larvae;H. Five-year-old larvae that have just molted (top) and matured (bottom). (Source: Journal of Biological Resources, Yilan University)
No 4. The history of butterfly's lifelong struggle
Through some of the above stories, we have a general understanding of the poisoning strategy of the butterfly larvae stage, so how does it achieve a foolproof self-protection strategy throughout the life of the butterfly? How did these strategies evolve, and how did they evolve? This is the focus and content of this article.
Some of the above basics about butterfly defense are easy to understand. However, the butterfly is a completely metamorphosed insect that goes through four completely different stages of life, eggs, larvae, pupae and adult. In the larval stage, it needs to molt many times, some up to seven or eight years old, and the life history is quite complicated. In the picture below, the butterfly, whose form and color change throughout her life, is more magician than a magician.
Life history of Papilio zelicaon (eggs, newborns, L1, L2, L3, L4, L5 generations, pre-pupae, pupae, male adults, mates, spawning)
Here, we would like to throw out an interesting scientific question: in the evolution of the butterfly, is the evolutionary relationship consistent at each stage? What codes and secrets does nature use to control their development and evolution?
Modern science, or ecology or natural history, has already entered a very complex stage, and this problem is one of the most common scientific problems. Only with a considerable background knowledge can we understand what scientists are studying and thinking about today. Is the complex development process of insects in the family Phyllonorycter family from caterpillars to butterflies, and is the evolutionary history of life constant? Such questions are often difficult to understand, abstract, and interrelated, and are easy to understand only if you have a considerable basic knowledge. The huge gap between modern science and public knowledge is the huge gap between science popularization and nature education that we are now carrying out. However, once you enter this evolutionary understanding of thinking, the perception of nature will enter a new world, which is very exciting. Back to the point, let's talk about the vagaries of defense strategies that caterpillars have throughout their lives.
Earlier, we've covered three defense strategies used by the butterfly caterpillar: masquerade, crypsis, and aposematism. Using data from 64 species of butterfly larvae and related hosts, Indian scientists made an interesting analysis of how different butterflies choose defense strategies.
The study found that in the first stage, when the caterpillar was a child, some were alert colors (orange red), some were hidden colors (green), and some were camouflage (blue), and it was known from the system tree that camouflage and concealment colors were evolved from warning colors. (As shown in the figure below)
Relationships between different young caterpillar systems and their defense strategies (orange is the warning color, green is the hidden color, and blue is camouflage)
In the second stage, as the small caterpillar grows, its motor ability increases, and the plump and juicy caterpillar also changes in body color and morphology, and some even change dramatically. Many of the butterflies in the upper right corner of the figure below have gradually changed from camouflage to hidden colors, choosing a low-key life of hiding themselves. From the system tree of the last larvae, it is known that camouflage can evolve into a hidden color. (As shown in the figure below)
Relationships between different end-of-age (grown) caterpillar systems and their defense strategies (orange is the warning color, green is the hidden color, blue is camouflage)
In the third stage, when the caterpillar has stored enough energy to pupate, the caterpillar almost loses the ability to feed and move, and at this time, something magical happens. Almost all pupae shed the arrogance (brilliant warning color) of the caterpillar, and instead turned into a low-key hidden green, hidden among the leaves, so as not to be discovered by predators. Combined with the system tree above and below, we can see that during the development from caterpillar to pupae, the warning color evolved into a hidden color.
Relationship between different butterfly pupa systems and their defense strategies (green is the hidden color)
Why does the butterfly larvae undergo such a wonderful shift in defense strategy from birth to growth to pupating into a butterfly?
Indian scientists analyzed the defensive color of the terminal caterpillar and found that the color of the original terminal caterpillar was related to the toxicity and background color of the food. Growing caterpillars, if they feed on sparse and poisonous plants, tend to be alert; if they feed on dense and non-toxic plants, they tend to be hidden; and throughout evolution, they show a historical process of mutual transformation between "concealment and camouflage" and "vigilance".
Systematic relationship between different terminal caterpillar defense strategies and plant toxicity and background color (inner dots indicate food resources: yellow is a poisonous and sparse plant, black is a dense and non-toxic plant) (peripheral dots indicate a terminal caterpillar defense strategy: orange is a warning color, green is a hidden color, and blue is camouflage) (font color indicates plant distribution: purple is a temperate plant, blue is a tropical plant, and black is a plant distributed in both temperate and tropical zones)
The philosophy of the butterfly struggle
The comprehensive description of the ecology and evolution of the caterpillar defense strategy above is like what The Taoists call "yin and yang" changes.
When plants evolve violent toxins, it will reduce the leaf content and form a sparse and toxic ecological environment; non-toxic plants will often grow many leaves to form a leafy ecological environment. The two environments are two different options for butterfly larvae.
Butterfly larvae hatch with a variety of strategies, including concealment, camouflage and vigilance. When its athletic ability is weak, choosing a warning color is undoubtedly a wise strategy. And butterfly larvae feed on such plants, they will choose to enrich toxins, warning birds and other good-sighted predators with warning colors;
The interrelationship between butterfly ecology and evolution is like a yin-yang system (orange is the warning color, green is the hidden color, blue is the camouflage)
As the caterpillar grows, its athletic ability is greatly enhanced, and at this time it also grows into a fat flesh, either choosing to continue to strengthen the vigilance ability, enriching more toxins through food, enhancing the ability to intimidate; or choosing a new path, shedding the amazing color of vigilance, choosing a green hidden color, and making a low-key caterpillar to protect it from the enemy;
When the caterpillar pupates, the pupae almost lose the ability to move to avoid enemies. At this time, hiding in the dense bushes and staying motionless is the best strategy.
The development, environmental adaptation and evolution of the butterfly are like two forces, in this complex ecological network, forming a dynamic evolution pattern, such as "yin and yang two forces", unification, opposition and interchange, forming the laws of nature: Tao sheng one, life two, two life three, three life all things.
Source: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences
Warm tips: Recently, the WeChat public account information flow has been revised. Each user can set up read-free subscription numbers, which will be displayed in the form of large cards. Therefore, if you do not want to miss the article of "Voice of the Chinese Academy of Sciences", you must do the following operation: Enter the "Voice of the Chinese Academy of Sciences" public number → click on the ··· Menu → Select "Set as Star"