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Dragon-lice
predaceous diving beetle
Overview
Also known as the diving beetle or true water beetle.
Carnivorous, aquatic beetles of the Coleoptera (Dytiscidae) family, with more than 4,000 species, feeding on organisms ranging from insects to fish larger than themselves. It is flat and ovoid, 1.5?over 35 mm (0.06?over 1.4 in) long. Adapted to aquatic environments, with flat, long, ciliated hind feet to expand surface area for floating and swimming, and ventral dorsal sheathed wings with valves underneath the tips to facilitate respiration. When at rest, tilt the head underwater and raise the end of the sheath wings to expose the valve for breathing. Before preparing to dive, air is stored under the wings for underwater breathing. The body is streamlined, some species of males have a sucker on the forelegs, when mating to crouch on the smooth back of the female.
The female lays her eggs in the water or on aquatic plants. Larvae are very large eaters, commonly known as water tigers, elongated, sickle-shaped palate. It injects digestive juices into the captured object through a tube in the palate and sucks up digested animal tissue. Like adults, they hang below the surface of the water and breathe through abdominal valves. In some species, the filamentous appendages on the abdomen of the larva act as gills, thus eliminating the need to go to the surface of the water to breathe. Pupate in wet soil.
Dytiscus and Cybister are two important genera with a cosmopolitan distribution, over 35 centimeters (1.4 inches) in length, and are reared and eaten in the East. The eyeless dragon louse (Siettitra) is eyeless and lives in deep wells. It is not a beneficial insect because it eats fish and competes with fish for space and food rather than being a major food source for fish.
Identifying Characteristics
The dragon louse is a Coleoptera, family Lepidoptera. Small to large, long eggs are streamlined, flattened, and smooth. Body dorsal-ventral surface arched, antennae filiform, 11-segmented, mandibular whiskers short. Head retracted into prothorax. Hind feet are swimmer's feet, posterior basal segments occupying a large portion of the ventral surface with the posterior thoracic ventral plate. Ventral surface of thorax without pinnae.
About 4000 species are known in the world, about 200 species are recorded in China, and the common ones are the yellow-margined dragon louse Cybister japonicus Sharp and so on.
Biological habits
Complete metamorphosis. Adults and larvae live in still or running water, and a few are found in brine or hot springs, both of which feed on mollusks, insects, tadpoles or small fish. Larvae are particularly voracious. Adults have phototropic, adult buttock glands can release benzoic acid benzene, steroidal substances on fish and other aquatic vertebrates have significant toxicity, can be harmful to rice seedlings and wheat seedlings.
The dragon louse, also known as the water turtle, for the dragon louse family of the size of the genus collectively, belonging to the insect order Coleoptera Carnivora, dragon louse family, is emerging in recent years to eat the precious aquatic insects, living in the field, ditches, streams and other bodies of water. It can swim in the water, fly out of the water, and has a strong tendency to light. Adult dragon lice have an oval body shape and are about 3 centimeters long. The individual size of the dragon louse varies, was streamlined body, to carnivorous mainly, but also eat plants and so on, especially good at catching small fish and shrimp in the water and aquatic insects for food. In China, mainly produced in Guangdong, Guangxi, Hainan, Fujian and Hunan, Hubei and other provinces and regions. At present, the market source of dragon lice mostly rely on the capture of wild resources, due to water pollution and man-made indiscriminate fishing, so the number of decreasing, so that the market demand exceeds supply, resulting in a more expensive price.
Although the price of dragon lice is expensive but loved by people, the reason, in addition to the fresh food taste delicious "and taste", it also has a high medicinal value. According to records, the dragon louse has nourishing Yin tonic kidney effect, on the treatment of pediatric enuresis, the elderly nocturia, as well as kidney deficiency, chancre, etc. have a good effect. Eat dragon lice to lower cholesterol, prevention and treatment of hypertension, obesity, nephritis, etc. also have a good effect. Long lice in addition to fresh food can also be processed into powder, dipping (such as lice wine), pills and other therapeutic products, so the market is very good, quite a farming development prospects.
There are many kinds of dragon lice, only in our country there are 160 species, of which the Japanese sucker dragon lice is one of the largest individual. According to the trial proved that the original wild lice can be artificially cultured, has been successful in our province and other places of culture. Long lice breeding cycle is short (from eggs to commercial adult about 8 months or so), dissolved oxygen, water temperature, pH and other requirements are not high, and it is less morbidity, a wide range of food, easy to farm management; long lice individual small, occupy a small space of the water body is also small, suitable for fish ponds and other water surface in the breeding, but also suitable for a few square meters of concrete pools or even the area of a smaller tanks, such as small bodies of water breeding; feeding costs are lower, you can collect the distribution of the local The feeding cost is low, can collect distributed in various places of the Fushou snail, snails, fresh dead fish and shrimp, slaughterhouse of various animal scraps, etc. directly into the pool feeding, and then occasionally will be corn meal, wheat bran and other energy feed mixed with water and wet kneaded into a ball, after the drying feeding. Therefore, all over the world can be based on market demand, actively study the development of breeding.
How do dragon lice reproduce and give birth to offspring? To sexual maturity and development, the male dragon louse will chase the female dragon louse, with its forefoot tarsal joints at the base of the expansion of the round sucker (hold feet) adsorption of the female dragon louse smooth sheath wings on both sides of the front, and climbed to the back of the body of the female dragon louse for mating. Thus, it seems that the dragon louse is still heterozygous (female dragon lice do not have suction cups on their front feet). The female louse lays her fertilized eggs on the water plants and hatches the small larvae by the temperature of the water. Small larvae do not have air sacs, only by the body of the trachea storage of very little air, so the incubation time in the water can not be too long, often swim to the surface, the end of the belly of the trachea exposed to the surface of the exhaust, inhalation of fresh air. The larvae of the dragon louse feeds on small fish, tadpoles and other animals, but it has no visible mouth and its upper jaw does not have the function of chewing food. Its upper jaw is hollow, with a small hole at the base that secretes digestive substances and connects the mouth and esophagus, and a small opening near the tip that sucks up liquid food. When catching prey, it first spits out poisonous liquid from the esophagus and injects it into the prey through the hollow upper jaw to anesthetize it, and at the same time spits out liquid with strong digestive function to dilute the substance in the prey, and then sucks up the digested substance. Therefore, the feeding and digesting method of dragon lice larvae is called parenteral digestion.
Dragon lice habits: carnivorous, ferocious gluttony. Said it ferocious, because not only eat small fish, shrimp, insects and tadpoles, even the volume than their own several times the fish, frogs will also go to the attack to feed on prey, but the prey was bitten, the neighborhood of the dragon louse smelled blood will swarm up. It is said that it is voracious because as long as there is food, they really eat to the point of holding on, floating in the water can not even float, but no big deal, it is in the water for more than an hour, it will produce a gas exchange bubble in the tail, underwater gas exchange. Its larvae resemble centipedes and are also ferocious and voracious. Preying on other small insects, it is not surprising that it eats 15 tadpoles a day and night.
Superior diving skills
The human underwater work or deep-sea investigation, usually done by divers. Divers need to carry oxygen and a set of equipment to maintain a relatively long period of underwater work. Insects also have a lot of diving masters, the dragon louse is one of the outstanding category, it can dive into the bottom of a very deep pond for a long time. Even in winter, it can lurk for a long time at the bottom of the water under a very thick layer of ice, and will not die of asphyxiation due to lack of oxygen. After the winter, the ice melted, it is the end of the underwater wintering lurking life, began to swim freely in the water. Its ancestors originally lived on land, and later evolved into aquatic due to changes in the earth's crust, so it still retains the characteristics of its ancestors breathing air. In the dragon louse sheath wings below an air sac, this air sac has a "physical gills" function, when the dragon louse in the water up and down when it also plays a role in positioning. Lice stop in the water, the front wings gently shake, the body with carbon dioxide exhaust, and then use the contraction pressure of the air sac, from the air to absorb fresh air. The oxygen content in the air is many times more than in the water, so aquatic insects in the long-term evolutionary evolution process, learned a variety of ways to absorb air. Dragon lice rely on stored fresh air to dive into the water to live. When the air sacs run out of oxygen, and then swim out of the water, re-exhausted exhaust, inhale fresh air.