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Dragonfly, invertebrate, Insecta, Odonata, Arthropod, generally speaking, it has a large body, long and narrow wings, and the membrane and reticulation are extremely clear. Vision is extremely sensitive, with 3 eyes; Antenna 1 pair, thin and short; Chewing mouthparts. The abdomen is slender, flat or cylindrical, with anal appendages at the end. Feet are thin and weak with hooks and thorns, which can catch pests when flying in the air. Larvae (larva) develops in water and breathes through rectum, trachea and gills in water. Generally, it takes more than 1 1 times to molt, and it takes more than 2 years to climb out of the water along the aquatic plants, and finally molt and emerge as adults. Larvae can prey on old and other small animals in the water, and sometimes the same kind will eat each other. Adults usually fly in ponds or rivers and prey on flying insects. In addition to a large number of harmful insects such as mosquitoes and flies, they are beneficial insects, and some can prey on butterflies, moths and bees. There are more than 5000 known dragonfly species.

External physical characteristics

Dragonflies can be divided into Diptera of dragonflies and Homoptera of damselflies. There are only three kinds of dragonflies in China, which are called living fossils and are the oldest dragonflies in China. It is also a very primitive insect in winged subclass. Larvae is called larva, completely aquatic, and its morphology and habits are completely different from those of adults. The larval morphology varies greatly.

dragonfly

dragonfly

Dragonflies have flexible heads and short antennae.

Dragonflies are the insects with the most eyes in the world. Dragonflies' eyes are big and bulging, occupying most of their heads. They have three single eyes and consist of more than 28,000 small eyes. Their eyesight is so good that they can look up and down without turning their heads. In addition, their compound eyes can measure speed. When the object moves in front of the compound eye, each "small eye" reacts in turn, and the moving speed of the target object can be determined after processing. This makes them master insect catchers in the insect world. Its chewing mouthparts are developed and powerful.

Dragonflies have developed wings, the front and rear wings are equally long and narrow, the membranous and reticular wings are extremely clear, and their flying ability is very strong, reaching 10 meter per second. They can suddenly turn around, soar into the sky, and sometimes fly backwards. When resting, put your wings flat on your sides or stand upright on your back. The front wing is not like the rear wing, which is often larger than the front wing. There are 1 wing moles near the leading edge and top of the wing, which are rectangular or square, which can keep the vibration regularity of the wing and prevent it from breaking due to vibration. Oblique chest, small chest, can move. Feet are close to the head (easy to prey) and the abdomen is slender. Although the structure of adults is quite consistent, the size is very different, and the wing spread is generally 5 cm. From the smallest 1.8 cm (0.7 inches) to the largest 19.3 cm (7.5 inches).

Dragonflies have a slender, flat or cylindrical abdomen with anal appendages at the end. Feet are thin and weak with hooks and thorns, which can catch pests when flying in the air. The male copulator is located on the second and third webbed abdomen. Male and female mating also takes place in the air. When most females fly on the water, they will "dot" their eggs in the water several times, and some will put their bellies into shallow water to lay eggs at the bottom of the water.

Dragonflies are not completely abnormal insects. The juvenile "hydra" lives in the water, breathes through the rectum, trachea and gills in the water, and preys with the extremely developed face cover. Generally, it takes more than 1 1 times to molt, and it takes more than 2 years to climb out of the water along the aquatic plants, and finally molt and emerge as adults. Larvae can prey on old and other small animals in the water, and sometimes the same kind will eat each other. Adults and larvae are carnivorous and eat many pests. Adults can not only prey on mosquitoes and flies, but also pests such as butterflies, moths and bees, so they are beneficial insects. I like to fly back and forth at low altitude before it rains.

Growth and reproduction

larval stage

Larvae breathe through gills. Usually, when the prey approaches, it will shoot a lip that can wrap the prey.

During the development process, the molting is 8 ~ 15 times, and the molting times within and between species are different, and there is no pupal stage. A few minutes after hatching, the sheath-like epidermis of the first instar larvae splits, releasing the spider-like second instar larvae, and the first instar larvae feed on aquatic animals such as crustaceans and protozoa. In the later stage, larvae eat chironomid larvae, water beetles, snails and even small fish. Wing buds appear in the early stage and grow with the increase of molting times. By the last age, adult organs have been formed in the body. A few days later, the larvae climbed out of the water, molted and emerged into adults (emergence). The biggest dragonfly usually leaves the water after sunset and takes off before sunrise, so it is rarely seen. Smaller species appear during the day. The newly emerged adult has soft body, immature reproductive system and imperfect color. One of its first activities was to fly out of the water. The life span of adults is divided into two stages: the first stage, about 2 days to 2 weeks, varies with species and climate; The other is the reproductive period, about 1 ~ 6 weeks. In the first stage, feed actively and stay away from water. The second stage begins with sexual maturity, when dragonflies fly to mating places (usually ponds and rivers, where they can lay eggs). The male bird arrived earlier, occupied a certain position on the river bank or water surface, defended his territory like a bird, and drove away other invading males. If a female bird flies near or into the field, the male will try to mate with it. Some species courtship before mating.

mating season

The mating posture is unique. The male holds the female's head or chest with the gripper at the end of the abdomen, and through its action, induces the female to bend the abdomen forward and touch the copulatory organ at the base of the male abdomen. When mating, land on the ground, but it can also be done in the air. Mating time varies from a few seconds to several hours. Females lay eggs immediately after mating, or after several hours or days. There are two ways to lay eggs. Developmental ovipositors lay eggs in or on water or aquatic plant tissues, and some climb to the surface to lay eggs, which can be soaked in water for more than 1 hour. The head can rotate flexibly, 1 has compound eyes, is large, and has no ovipositor to wash the eggs from the ventral end into the water. There are several kinds of running water spawning, but there are attachment or winding devices to prevent them from being washed down. Adults need a warm climate, food suitable for spawning and water to reproduce. Fish and birds will prey on dragonfly larvae, and larvae will devour each other. When it appears, it may be preyed by birds and small crocodiles. However, after leaving the emergence scene, the adults are almost harmless, flying quickly and flexibly, and can avoid almost all enemies. Most species in temperate regions overwinter with larvae, the larval stage can reach 1 ~ 5 years, and the life span of adult stage is only a few weeks.

womanhood

The eclosion adults have different colors, and the chromaticity varies from metallic color to pink. Compared with other insects, it is huge. Some species have a wingspan of 16 cm (about 6 inches), and even the smallest species has a wingspan of 2 cm (0.8 inches). Besides being extremely agile flying animals, they are also one of the fastest insects. Dragonfly wing muscles can only function best when it is warm, but if the weather is cool, this insect often expands its wings to generate heat before taking off. Dragonflies' speed and agility make them the most efficient flying predators. The prey is usually flying insects, but some dragonflies often eat 60% of their own weight.

Young dragonflies-called larvae, semi-metamorphosed through incomplete metamorphosis, sometimes called larvae-are aquatic animals and special predators in water, just like adults in the air. Functional wingless larvae are usually mottled or dull in color, just like sediments or aquatic plants in their living environment. Their prominent eyes are similar to those of adults, but they have amazing anatomical structures that adults do not have. This is called "mask", which is the fusion of the third pair of mouthparts of larvae. Masks are disproportionately large and are placed under the head and throat when not in use. At the end of the mask is a set of toothed clips, which are used to catch worms, crustaceans, tadpoles, small fish and other prey. Different kinds of dragonfly larvae are called creeping insects, burrowing insects, hiding insects or trapping insects-their body shape, metabolism and respiratory terminal depend on their micro-habitat.

When larvae crawl out of the water or eggs are in the water, there are three ways to produce eggs. Some species lay eggs in plant tissues, while others attach eggs to the bottom or top of surface water. Eggs may also fall from the abdomen or be washed into the water. Larvae use gills in rectum to draw oxygen from water. Water is sucked into the abdomen and then pressed out through the anus. Water may be forcefully discharged in this way, thus creating an escape method of jet propulsion. Solid waste is also discharged in this way. As the larva grows up, it will shed its skin, and about half of its future wings will first become obvious during the growth of the larva. Then, these wing sheaths increase rapidly in the subsequent molting process. Finally, the larvae climb out of the water (sometimes at night), shed their skin for the last time and become adults, leaving a layer of skin (molting shell), which is the shell of the body in the past.

The mating of dragonflies also takes place in flight. Male dragonflies grasp the neck of female dragonflies with hooks at the end of abdomen; The female dragonfly's abdomen bends from bottom to front, connecting the reproductive hole with the sperm storage organ below the second section of the male dragonfly's abdomen, and then the male dragonfly is fertilized.

Why do dragonflies drink water with their tails?

Dragonflies are different from many other insects. Its eggs hatch in water, and its larvae live in water, so it is actually laying eggs when it comes into contact with water. Female dragonflies lay eggs in the water, and most of them touch the water with their tails when flying, so as to expel the eggs. Our common so-called "dragonfly water" is its performance when it lays eggs. The eggs of dragonflies are yellow.

Dragonfly is a typical incomplete metamorphosis insect, and it does not need to go through the pupation process from larva to adult. They only go through three stages in their life: eggs, larvae and adults. Dragonfly larvae are aquatic, while adults are terrestrial insects with flying ability.

egg

Dragonfly eggs will be placed in plants, dead trees or even dry soil, or they will be thrown on the water at will according to their species. The eggs of most dragonfly species in temperate regions do not hatch immediately after delivery, and it may take several months to hatch larvae. This period of non-incubation is called "diapause period", which aims to let dragonflies spend the cold winter in the form of eggs. Because of the mild winter climate in Hong Kong, this phenomenon does not necessarily exist in Hong Kong, but it is known that some species of Dracaena that lay eggs in dry soil can generally survive in the form of eggs for a period of time in dry environment. The eggs of yellow ducklings hatch only in feces. They can hatch in short puddles formed after rain. Their rapid growth is obviously a good advantage.

Female swimmer

The first stage or age of hatched larvae is called pre-larvae. They have no feet, and this stage usually lasts only a few seconds to a few minutes. After molting for the first time, the larvae enter the second instar. They have simple feet and three connected antennae. The growth period of larvae is generally eight to fifteen years old, which is the longest time in the life of dragonflies.

Larvae go through a metamorphosis period before they grow into adults. At this stage, the larvae will become adults, but they will remain in the exoskeleton until the last age. During this period, the body of the larva will slowly rebuild into an adult in the exoskeleton. Because the mouthparts gradually degenerate, the larvae will stop eating. When the colors and stripes on the adult body can be seen through the larva's shell, the larva will soon emerge at the right time. Dragonfly adults will appear directly from mature larvae, and they have well-developed wing buds. Dragonflies have no pupa stage. Changing from larva to adult is a very special process, because there is no similarity between the two stages.

emerge in large numbers

In areas with mild climate, winter limits the emergence period to spring and summer. In view of the subtropical climate in Hong Kong, the winter is short but obviously cool, which makes the emergence period of most dragonfly species have no obvious regularity. Some varieties in Hong Kong are called "spring varieties". They emerge as adults in spring, and the peak of emergence is usually in late April or May. They have a synchronous emergence pattern, that is, the rainy season begins, the temperature rises, and their emergence period begins. Spring varieties include most of the river-dwelling spring Odonata, such as the one-horned spring Odonata and the pure-tailed spring Odonata. The emergence period of these two dragonflies is about two weeks earlier than that of China dragonflies. Tabanidae are also spring varieties, and their flight time is very short. On the other hand, from spring to the end of 1 1 month, they can be seen spreading their wings and flying. Dragonfly species with no obvious pattern in the emergence stage can mostly see flying from March to the following year 1 month. Due to the influx of migrating population, yellow ducklings fly all year round. However, this situation is unlikely to occur in 1 month and February, because although it is estimated that the migrants will come from the Philippines, the prevailing winds in these two months mostly blow from the east or northeast, and rarely from the Philippines in the south.

Some species, especially the blue striped duckling, will not be seen until late summer, but most of them are in spring. In summer, there will still be larvae, but the number will gradually decrease. In late autumn, the emergence period will be completely over, which is related to the obvious drop of the average temperature at that time.

The actual process of eclosion is very exciting, usually completed within one hour. However, it may take several hours to harden the soft body and shiny soft wings and turn them into fully mature colors. During this time, they can't move and lack hard shell protection, so dragonflies usually choose to appear from dusk to early morning to reduce the chance of being hunted. However, in the process of eclosion, if you are not careful, your body or wings will not be fully unfolded because you hit the surrounding objects, leading to deformity, affecting your future mobility and even death. Most dragonflies begin to emerge in the evening shortly after dusk, and then make their first flight before dawn. Spring Dragonflies, Odonata and Amphibia all appeared in the early hours of the morning. Dactylogyrus species appear at night.

type

Dragonfly breeding is the most distinctive, and the evolution of this breeding method is still a mystery. Like other insects, the reproductive organs of dragonflies are at the end of the abdomen.

The ventral surface of the ninth abdomen. Before mating, the male will transfer the sperm from the genital hole to the second group of sexual organs located on the ventral surface of the second and third abdominal segments, and store the sperm there. Mating begins when the male catches the female who is willing to mate. First of all, the male will bend the abdomen and use the mating process of the anal appendage at the end of the abdomen to grab the back of the head or the chest backboard of the female. Then, the male will loosen the grip of his feet on the female and let the female hang easily at the end of the male's abdomen. The female who is willing to mate will bend her abdomen to make contact, and the end of her abdomen will cling to the male's second sexual organ. This mating pattern is sometimes called "wheel" in English. Then, the male will take out all the sperm left by the female in the past mating, and then put his own sperm into the female with penis-like organs.

The anal appendages of male insects and the back of the head of female insects, as well as the second sex organs of male insects and female insects, coordinate with each other like locks and keys, which are unique to this species. Because of this subtle feature, the chances of mating between males and females of different varieties are greatly reduced. However, sometimes some careless males catch the wrong person. Therefore, the structure and characteristics of anal appendages are the best criteria for classifying and distinguishing varieties. Some Odonata insects may only need a short time to mate, but for most species, mating is a very long process, and it takes a few minutes or even hours for females to lay eggs.

Most females lay eggs immediately after mating. When laying eggs, some females will be "connected" by the male holding the back of the abdomen; Others will not be caught by males when laying eggs. Many males protect females when they lay eggs, even if they don't hold them tightly in case other males are interested in females. Some dragonflies put their eggs in plants, which is called "endogenous spawning"; Others will drop their eggs on wet plants or water at will.

distribution range

Blue-faced dragonflies and other common dragonflies are mostly distributed in Zhejiang, Sichuan, Guizhou and other provinces; Green dragonflies with moles are distributed in northern China. Huang Qing has many provinces, municipalities and autonomous regions in China.

Have distribution; Jade Dragonfly is only produced in China, mainly distributed in Beijing, Jiangsu, Fujian and other provinces.

Species introduction

There are about 5,000 species and about 300 species in China. The most common dragonflies are all kinds, such as Biwei Pavilion, Yellow Duck Pavilion, Long Leaf Nevus and so on. These three species basically represent various families of dragonflies, namely, large dragonflies, medium dragonflies and damselflies.

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Classification status

The taxonomic status of Insecta, Insecta Odonata, Anioptera, the smallest suborder of Dragonflies, has three genera and three species. The characteristics of Mesoptera are between Homoptera and Heteroptera. Features: Insects are of medium size, large head and flexible rotation. Two pairs of wings have transparent membranes, multiple transverse veins, and there are wing moles near the top of wings. The abdomen is slender, and the male copulator is born on the ventral surface of the second and third abdominal segments. The wing base is not pedunculate, and the rear wing is larger than the front wing.

There are only three species, one from the south of Himalayas, one from Japan and one from the southeast of Heilongjiang Province (new species published on 20 1 1). It is the surviving offspring of the ancient γ τ group and is called a living fossil. From 20 1 1 to 20 12, 1, through the joint and collaborative research of German, China, Laos, Nepal and Japan, and through the systematic analysis of the DNA of the three known species of Epiophlebia in the world, it is concluded that the new species found in Heilongjiang Province, China is older than the known species distributed in the southern Himalayas and Japan. Through the research of scientists from many countries, it is found that this kind of dragonfly is older than Japanese dragonfly and Indian dragonfly in the evolutionary tree. This was an important discovery in the insect world last year. It is named the life habit of Odonata in China, and its morphology is between Heteroptera (Odonata and Odonata) and Homoptera (Myrtaceae). The body is close to dragonfly, but the structure of front and rear wings is close to damselfly. Dragonflies are very common in ancient times, and dragonfly fossils are often produced in Northeast China, but they are gradually scarce after Cenozoic.