Dragonfly insects are closely related to humans, and in the ponds of the park, we often see "dragonflies dotting the water". Most dragonfly insects are beneficial to humans because their adults catch mosquitoes or flies, but it is worth noting that the larvae of dragonflies have a greater impact on fisheries, and their larvae live in the water and catch small shrimp or fry to eat.
Larval predation
The juvenile insects of dragonfly insects are called waterflies. The most peculiar organ of its head is the lower lip part of its mouth organ. Their lower lip is strongly specialized and is called a lower lip mask, or face shield. The lower lip hood is divided into two parts and can be folded. In the absence of predation, the lower lip mask folds and shrinks to cover the entire mouth organ, looking like an alien monster.
Oysters lower lip
When encountering prey, the waterhopper will eject the lower lip cover and use the jagged structure of the front end to grasp the shrinking lower lip cover and drag it back to the mouthpart for feeding. This specialized lower lip mask also helps the dragonfly baby gain a huge survival advantage in the water.
The thorax of the baby is born with 2 wing letters that will develop into wings in the future. There are also 3 pairs of feet on the thorax, and some dragonfly insects also have a short protrusion on the outside of the forefoot and the end of the middle foot, called a digging hook, which plays the role of digging the bottom sand in the water. The abdomen of the juvenile is 10 segments, most of which are ridged or prismatic cylindrical. At the end of the abdomen of many waterhoppers, there will be some spine-like structures called lateral spines. The abdomen of the baby worm also has some respiratory organs, but the respiratory organs of different dragonflies are very different.
abnormity
The head of the dragonfly insect is born on the front chest and can be rotated very freely. The whole head area is more obviously divided. Viewed from the front, from top to bottom are the back of the head, the top of the head, the forehead, and the base of the lips. The antennae are bristle-shaped and consist of up to 7 segments. The compound eye is well developed and consists of a very large number of small eyes, which play a very important role for dragonflies to find prey and avoid predators. On the top of the head, there are 3 single eyes. The mouthpiece is a chewy mouthpiece and is fully developed.
Dragonflies have 3 pairs of feet on their thoraxes and often have a large number of long and short spines. More specifically, although the thorax of the dragonfly is divided into anterior chest, middle chest and posterior chest, the middle chest and the posterior chest are closely healed together, and the two segments cannot be rotated, which is called a closed chest. The thawed breast is the strongest part of the dragonfly's body , on which two pairs of unusually developed membranous wings grow. Most dragonflies have transparent wings, but there are many species that have various spots and patterns on their wings. Dragonflies have very dense and complex wing veins, which form many closed wing chambers, and at most even have more than 3,000 wing chambers on one wing. The vast majority of dragonflies have a thickened opaque marking near the front of the wing called a winged nevus. It is also one of the most distinctive features of dragonfly insects. The shape and length of winged nevi vary according to the taxa of different dragonflies, and some dragonflies have no wing moles or only one pseudo-winged mole on their wings, such as many groups of insects in the family Offidae, the males do not have wing moles, and the females have only one false winged mole, or pseudo-winged mole.
The abdomen of dragonfly insects is slender and cylindrical, forming a very complex secondary reproductive organ called a mater in the 2nd and 3rd abdominal segments of male dragonflies. At the end of its abdomen, there is a well-developed upper appendage and a lower appendage, which plays an important role in clamping the female insect during mating. Female dragonflies have ovipositors at the end of their abdomen, and the shape and size of the spawners vary significantly according to different dragonfly species and spawning methods.
When dragonfly insects leave the water body and feather into adults, they usher in the most important stage of reproduction in their lives. The locations where they court and mate are inextricably linked to the water systems in which the baby insects live. However, adults of dragonfly insects do not inhabit the water system directly, and many species are free to choose their habitat after just feathering, until they are sexually mature and fly back to the water's edge near the breeding season. Males usually return to the water's edge before the females and occupy a territory for a long time, and are driven away by other dragonfly individuals if they enter. When the female appears next to the water system, the male will chase and court the female. Different dragonfly species courted in different ways, and some dragonfly males would fly in front of the stopped females and use the white and purple metal spots on the inside of the mid and hind feet to sway in front of the females to achieve the purpose of courtship. There are also males who make their body color unusually bright during the breeding season to attract females.
Mating of dragonflies
When dragonfly insects begin to mate formally, their mating method is also unique among insects. At this time, the male will use the appendage at the end of his abdomen to clamp the female's forethia and slightly clasp the inside of the female's compound eye, while the female will bend the abdomen forward to connect the reproductive hole between the 8th and 9th abdominal segments of the abdomen and the paragenitum of the male 2nd abdominal segment. At this time, the entire male and female insects are connected into a love-like ring, whether they are parked on the vegetation or in flight, the two are not separated. Although male and female worms are connected to each other for a long time, the time for actual insemination is only a few seconds. Many male dragonflies do not leave immediately after mating, but continue until the female has laid eggs.
Mating process
The vast majority of female dragonflies have egg layers, which produce "point water" in the form of point water Some species directly discharge the eggs into the water, allowing the eggs to sink naturally into the water, while the macrosic family erects the entire body and violently pokes the sediment into the bottom of the water with the egg layer, and lays eggs here. To distinguish it from the spot water spawning of the dragonfly family, the spawning method of the macrospermenophalus is also known as "planting spot water".
Other dragonfly females will fly along the surface of the water and sprinkle eggs or egg masses into the water in the form of airdrops. Although this spawning method has been reported many times in some literature, it is difficult to verify. This spawning method is called "airdropping".
Wildlife conservation science states that we should scientifically protect a wide variety of species. Dragonfly larvae live in water, adults live on land, and all of them are carnivorous, so they play a very important role in the population control of onshore insects and other animal-free animals. In addition, because many dragonfly insects have high requirements for water quality, their number can directly reflect the changes in the quality of the local water environment, so it is also known as water quality monitoring insect taxa, which undoubtedly plays an important reference role in environmental protection. Due to the acceleration of urbanization, some ponds and streams have been destroyed, which has also allowed some dragonflies to almost disappear in the city.