A nail in the tail, two beans in autumn water, hairless wings and no feet, can't walk and hit a bug.

A nail in the tail and two beans in the eye. Wings without hair and feet without walking: dragonflies.

Dragonfly (scientific name: dragonfly), alias Dengdianer, Leech, Odonata, Odonata, beneficial insect. Common dragonflies such as blue dragonflies are distributed in Zhejiang, Sichuan, Guizhou and other provinces, green dragonflies with moles are distributed in North China, and jade dragonflies are only distributed in Beijing, Jiangsu and Fujian.

Dragonflies are generally large in size, with long and narrow wings, three eyes, 1 pair of antennae, thin and short, chewing mouthparts, slender, flat or cylindrical abdomen, anal appendages at the end, thin and weak feet and barbs. 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.

Morphological characteristics:

The shape and pulse sequence of the front and rear wings are different; Wing base is not stipitate, not obviously long and narrow; The medial cavity is divided into triangular cavity and upper triangular cavity by oblique veins, which usually have different shapes on the front and rear wings; Two compound eyes touch or are separated by a thin seam; Male 1 anal appendage; At rest, the four wings extend horizontally to both sides. The research methods of flight mechanics of dragonfly wings are also constantly improving, from tying with ropes to shooting with high-speed cameras and then observing in wind tunnels. More and more advanced methods make the study of dragonfly flight mechanics deeper.

Dragonfly's research on dragonfly wings mainly focuses on mechanical principles and bionics. Dragonfly wings have two special structures: wing knots and wing moles, which make it an excellent flier in nature. In the study of mechanics, it is found that the dragonfly's wings will be affected by horizontal force, vertical force, moment, bending and movement when flapping and turning in the air, and it is found that the slow flight of dragonfly is very similar to that of an airplane.