The distribution of insects is so wide that no other class of animals can compare with it, almost all over the earth. There are different species. Most insects can be used as specimens and are good biological resources that can be used by human beings. Here are the 100000 whys I carefully recommend: why do insects peel? It's for reference only. Welcome to read!
Why do insects peel
Molting of insects is necessary for growth, because the epidermis (exoskeleton) of insects is composed of waxy layer and chitin layer. The wax layer is located at the outermost layer of the surface layer, which can prevent the evaporation of water.
Chitin is a complex nitrogen-containing polysaccharide, which is the main component of exoskeleton. Below the chitin layer are epidermal cells that secrete exoskeleton. Once the exoskeleton secreted by epidermal cells is hardened, it cannot continue to expand, which limits the growth of insects. Therefore, molting occurs during the growth and development of insects. During molting, epidermal cells secrete an enzyme to dissolve chitin, and the wax layer breaks. Insect larvae can drill out of the exoskeleton and secrete the exoskeleton again by epidermal cells. When the new exoskeleton is not completely hardened, the insect body can grow. The hardening of exoskeleton is due to the denaturation of protein. Therefore, the developing and rapidly growing insect larvae molt more often. Molting stops when insects stop growing. After the last molting of completely metamorphosed insects, the secretion of ecdysone is normal, the secretion of juvenile hormone decreases and enters the pupal stage.
An insect hatches from an egg into a larva. During the larval stage, it needs to peel off several times, and each time it peels off, it will increase one instar, just as higher animals grow up for one year. The newly hatched insect from the egg is called the first instar, the second instar after taking off the first skin, and the third instar after taking off the second skin. Push down this way, and add one to the number of larval peeling, which is the instar of the larva.
Why do insects peel? Because insects do not have the bone system of higher animals, they rely on the shell outside the body to play the role of skin and bone. This kind of body shell is also called exoskeleton or body wall. Although the body wall ensures that the insect can better adapt to various natural environments, its thickness is different in all parts of the insect body. Some thick and hard places are ossified and lack elasticity. When the larva grows to a certain stage, the growth of the insect is limited, it needs to take off the old skin and replace it with a new skin to continue to grow.
Insect peeling is an indispensable part of its life. Each peeling of insect larvae not only enlarges their bodies and further develops their internal organs, but also changes their external morphology. In addition, because the insect skin is formed by the products of metabolism, peeling also has the function of excretion. The growth and morphological changes of insect larvae show certain regularity due to peeling. For example, pink butterflies that harm vegetables peel! Times.
The process of changing the coat of insects is controlled by the endocrine organs in the body. When the insect grows to a certain extent, it secretes a kind of skin hormone, which separates the old epidermis and dermal cells of the insect, and gradually forms a thin new epidermis. Finally, the insect shrinks the abdominal muscles to increase the blood pressure of the chest and arch the back upward. Therefore, the old epidermis comes out along the particularly fragile place on the back of the chest. For example, when the cicada peels, it splits from the "" shaped place in the center of its back, wriggles from the outer skin, starts with its head and then its tail, and slowly climbs out. Insects living in water expand their body after absorbing air or water. It also splits in the particularly fragile place of the old skin, and then wriggles out of the soft insect body.
How do starfish eat
We usually think that gentle animals are herbivorous and fierce animals are carnivorous. So, these quiet almost motionless starfish should be more suitable for eating seaweed or plankton! On the contrary, starfish are not only predators, but also fierce predators. Of course, they don't attack their prey with lightning speed like cheetahs or sharks, but they can slowly approach their opponent and give their opponent a close hug with a tube foot with a suction cup. Sea animals such as crabs, shellfish and sea urchins are often wrapped in starfish. So how do starfish eat the food after they wrap them?
We know that animals cannot eat without opening their mouths. So where is the mouth of starfish? Turn the starfish over and you can see that all the step belt grooves of the starfish converge to the middle point, which is connected to the mouth of the starfish. The mouth of the starfish is located directly below the body disk, and the mouth surface is downward, which can be in direct contact with the surface of the object that the starfish climbed over, which provides conditions for the starfish to prey. However, when starfish eat, the mouth is only a channel, and the stomach is the real "murder weapon".
Because starfish have no eyes, they rely on a variety of chemical receptors to find food. When they slowly approach the prey and quickly catch the opponent with the tube foot on their wrist, they will wrap their whole body around the prey, and then spit out their stomach from their mouth. Next, digestive enzymes in the stomach are quickly released to the prey, dissolving the prey and sucking it in. This digestion is called in vitro digestion. The whole process is similar to that of spiders spitting digestive juice on food and dissolving it before absorption.
If the prey is a shell animal, the starfish will fix the body above the shell, suck both sides of the shell with two wrists, pull the shell of the bivalve hard through the suction cup at the end of the tube foot, and then spit out the stomach from the mouth and insert it directly into the opening of the prey shell. When the opponent's internal organs and adductor muscles are digested and dissolved, the whole shell is naturally opened. Starfish can easily wrap food in their stomach and inhale it into their mouth for final digestion.
Of course, not all starfish eat like this. Some starfish species with short wrists or tube feet without suction cups cannot resist powerful prey. They feed on smaller crustaceans and other animals and swallow their opponents. At this time, their digestion mode is different from that of most kinds of starfish. Their digestion is not in vitro, but directly in the stomach, which is called in vivo digestion. There are also some starfish living in the deep sea, which are directly "drunk" and eaten after filtering food particles with their fine cilia. Although starfish are small, they eat a lot. A young starfish eats more than half its own weight in a day.
The different feeding patterns of starfish are related to their living environment, which is the expression of biological adaptability.
Are butterflies beneficial insects
The so-called pests and beneficial insects are for people. Those harmful to people's production and life become pests, beneficial insects are beneficial insects, and others are classified as neutral insects. Butterfly larvae must be Lepidoptera insects. If they do harm to our production and life in the field, green belt or nursery, they must be classified as pests. But if in other places, it does not affect our lives, it can only be called neutral insects. After becoming adults, some butterflies stop feeding until they die after mating, which is also called neutral insects. The other part feeds on nectar, which is beneficial insects.
In fact, there are not many kinds of butterflies that cause material damage to human beings, such as rice Lane butterfly and rice eyebrow eye butterfly that harm rice, cabbage butterfly that harm cruciferous vegetables (cabbage), Yudai butterfly and citrus butterfly that harm citrus, camphor butterfly that harm camphor tree, and migratory pink butterfly that harm iron knife wood. Most butterfly adults are beneficial, such as spreading pollen for plants, maintaining ecological balance and beautifying nature. In addition, there are aphid grey butterflies that eat aphids, and other species that can be used for medicine or food.
There are few butterflies that will continue to harm plants after adults. If they affect people's production and life, they are still pests. Even if it hurts plants, it can not be regarded as pests. The difference between pests and beneficial insects is whether it endangers human production and life. If the number is under a certain base and the harmful plants are not closely related to human life, they can only be regarded as neutral insects. For example, are there any differences between locusts and grasshoppers? When they gather together, they are called locusts and do great harm. Artificial breeding, when used as feed and food, is a beneficial insect. There are absolutely no pests, absolutely no beneficial insects. The same is true of butterflies. Human beings are self-centered. Beneficial to human beings is beneficial to insects, and harmful to pests. Therefore, it can only be defined in a specific environment.