Water-spotting flying dragon—dragonfly

Dragonflies have slender bodies, bright colors, elegant postures, flexible and agile flight, interesting and attractive. They are people's favorite ornamental insects, often active in fields, gardens and other places during the day. Most dragonflies are 30 to 90 mm long, with a few species reaching 150 mm, and some species being very slender, with a body length of less than 20 mm. The idiom "dragonfly touches the water" that people quote actually refers to the phenomenon of female insects laying eggs after mating. Every time they touch the water surface, one egg is laid, and the action is very fast. People use this idiom to describe the meaning of work that is not in-depth.

Everyone is very familiar with dragonflies, and there are very few people who don’t know them. Dragonflies have been our play partners since we were very young. Nine out of ten children love to catch dragonflies, especially before or after the rain in summer, when swarms of dragonflies circle and dance in the low sky, which is very amusing. The children used branches, straw hats, brooms and even clothes to chase and beat them, and soon they had a pile of "trophies" in their hands. In fact, this kind of activity is really not worth promoting, because dragonflies are beneficial insects to humans, and both their adults and larvae are predators. All kinds of small flying insects are delicacies for dragonflies, including mosquitoes, flies, leafhoppers, small moths, butterflies, flies, etc. It is said that a horse-headed dragonfly can eat nearly 1,000 small flying insects in one day. . A dragonfly can eat 40 flies or 840 mosquitoes in one hour. One dragonfly larvae can eat more than 3,000 mosquito larvae in a year. Perhaps the children did not intend to harm the dragonfly, but they could not resist the temptation to play and did not understand the principle of protecting the dragonfly, so they did this. I hope they can find better ways to enjoy the cute little dragonflies in the future.

Types and Distribution Dragonfly belongs to the class Insecta, order Odonata, and its English name is dragonfly. There are about 5,000 known species in the world, and more than 400 species have been recorded in my country. Widely distributed around the world, most species live in tropical and subtropical regions. Dragonflies fly almost everywhere except the Antarctic and Arctic. Large dragonflies are mostly found in tropical areas. The Natural History Museum in London, England, houses a large dragonfly collected from Borneo, with a body length of 108 mm and a wingspan of 193.8 mm. There are two main suborders of dragonflies, (1) Homoptera (suborder Damselflies): The body is thin, the shape of the two pairs of wings is very similar, and the four wings stand upright on the back when resting. (2) Parapterygoid suborder (Odonata): The body is stout, the base of the hind wings is wider than the forewings, and the two pairs of wings are stretched flat when resting.

Interesting Reproductive Behavior On a hot summer day, I sat on the ground in the shade of a tree by the river. The gentle breeze suddenly dispelled many of the worries caused by the heat. I looked at the slowly flowing river, the slightly swaying water plants, and the light flying. The beautiful dragonflies and damselflies made me feel relaxed and happy. Well, look at that dragonfly's posture, it's so weird, its tail is bent back, as if it's eating its own tail. It turned out that it was a male insect. Since its copulatory organs are on the second and third abdominal segments, but the genital pore is on the ninth abdominal segment, the sperm must be moved from the genital pore on the ninth abdominal segment before mating. When it reaches the penis sac of the second segment, the phenomenon of "biting the tail" occurs. In summer, people often see two dragonflies chasing each other in the air, and after a period of time, they hug each other. That's sexually mature male and female dragonflies mating. Their mating method is very strange: the male dragonfly clamps the female dragonfly's neck or chest with its tail, and the female dragonfly flexes and extends the genitals at the end of the abdomen to attach to the mating organ between the second and third abdominal segments of the male dragonfly's abdomen for fertilization. They are like acrobatic stars performing a trapeze. I saw them hugging each other, suddenly landing on a leaf of water grass, and suddenly rising into the sky, flying freely. After the egg cells in the female dragonfly are fertilized and mature, it flies to ponds, lakes and other water surfaces, shuttles and flies from high to low, with a drooping abdomen, and the end of the abdomen is connected to the water surface, passing by, dotting as it flies, with gentle movements and posture Beautiful and quite ladylike. This is what people often call "dragonfly touching water". In fact, dragonflies lay eggs in the water and reproduce their offspring. Dragonflies lay their eggs in the water, and the eggs fall to the bottom of the water or attach to the surface of aquatic plant branches and leaves or other objects in the water. Some eggs are glued into strips and hung on aquatic plants.

The life history of a dragonfly. After a period of development in the water, the eggs hatch into larvae (larvae). Although it looks ugly, its mouth is very powerful. It has a very special device called a mask, or mask, which is a predatory organ formed by a specialized lower lip. It is very flexible and can quickly extend to capture prey. The end is equipped with a pair of movable hooks, which are extremely sharp. When the face cover is extended towards the prey, the pair of hooks quickly clamp the prey, the face cover is retracted, and the hooks bring the prey into the mouth. Dragonfly larvae especially love to eat mosquito larvae. One dragonfly larvae can eat more than 3,000 mosquito larvae in a year. Dragonfly larvae also defend themselves very effectively. The rectal gills in its body are not only used for breathing, but also help it quickly escape from danger when encountering enemies. The method is simple, that is, to quickly squeeze out the water entering the body, generate a reaction force, and shoot out the body at once. After 7-15 molts, which last from several months to several years, the larvae transform into adults - dragonflies.

Superb abilities ① The dragonfly's vision is very sensitive, and most of its head is occupied by a pair of large compound eyes. Each compound eye is composed of many small eyes, ranging from 100,000 to 30,000. Each ommatidium is a small camera, and the surrounding objects are continuously taken in to form images. It can see things within 6 meters. The entire compound eye is spherical, and its curved surface can take care of all directions. In addition, the dragonfly's big head can rotate freely, making the dragonfly's field of vision very broad. In addition to sensing object images, the compound eye can also measure speed. When an object moves in front of the compound eye, each ommatidium reacts in turn. After processing, the target object can be determined based on the images and time that appear continuously in the ommatidium. Movement speed. ② Dragonflies are flying experts among insects. Their wings are thin and light, weighing only 0.005 grams, but they can vibrate 30 to 50 times per second; their flight speed can reach 40.23 kilometers per hour, and they can sprint and fly. The speed can be as high as 40 meters/second. Look, its shape looks a lot like a small plane: four flat wings, a slender belly, and a smooth look when flying. The dragonfly is very flexible in flying. It can fly quickly, change direction and altitude quickly, and can glide slowly at a certain height, or suspend in mid-air. It can even fly upside down, sideways, straight up and down. It can be said that it is Call it what you will, even the most modern aircraft are nowhere near the flying prowess of the Dragonfly. Some dragonflies can fly long distances, spanning tens of millions of kilometers. The dragonfly's extraordinary flying skills should be attributed to its well-developed wing muscles and air sacs. The former allows the wings to flap quickly, and the latter stores air to regulate body temperature and increase buoyancy, so it can stay in the air freely. Its two pairs of membranous wings are covered with criss-crossing veins, making the dragonfly's wings both light and strong. There is a wing nevus formed by thickened horn on the front edge of the wings. Don’t underestimate this small wing nevus. It is a vibration absorber for the dragonfly’s flight. It can eliminate the vibration of the wings during flight. If you remove it, the dragonfly will fly. It will be swaying and erratic like being drunk. In the history of aviation, aircraft wings often broke due to severe vibration. Later, aircraft designers gradually found a solution based on the wings of a dragonfly, adding a counterweight to each wing of the aircraft.

Although dragonflies are powerful predators among insects, they cannot escape the fate of being harmed by their natural enemies. When it lives in the water, that is, in the egg and larvae stages, various fish, frogs, webbed birds and wading birds often pose threats to them. Even insects such as cantharides, waterside ants, dragon lice, Scorpion bugs, etc. will also attack them. Although the adult stage can fly far and high, it is difficult to defeat the more capable birds.

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