The weather is getting hotter and hotter, and annoying mosquitoes are becoming more and more active. If we stand by the river or the edge of the forest, we will soon be attacked by mosquitoes. How do mosquitoes find our position quickly? Several people live in a room with mosquitoes. Some people are often bitten by mosquitoes repeatedly, and some people are rarely bitten by mosquitoes or don't feel the existence of mosquitoes. These problems are what everyone wants to know and what insect researchers want to solve. After more than 30 years of unremitting efforts, the mosquito and fly department of the Insect Research Center of the United States Department of Agriculture finally uncovered this secret. In the 1920s, insect researchers knew that carbon dioxide exhaled by humans and animals would attract mosquitoes. In 1968, Ackery and others of Insect Research Center of Agricultural Service found that lactic acid in sweat can attract mosquitoes. However, these two compounds are not as attractive to mosquitoes as human arms when used alone or in combination. This proves that there must be other compounds that are mosquito attractants. When analyzing the components of fruit juice, researchers encounter difficulty in analyzing only a small amount of substances that volatilize into the air with sweat. A large amount of moisture in sweat is also a serious interference factor in the analysis. Now, the rapid development of micro-analysis and identification technology makes it possible for them to separate and identify this trace substance. 1999, Berner of the mosquito and fly department cooperated with the University of Florida to take samples by rubbing small glass beads with his palm and identify the components in sweat by gas chromatography-mass spectrometry. The advantage of this sampling method is that it can not only avoid the interference of a large amount of water in sweat on the analysis work, but also eliminate the interference of squalene released by human body on trace components. In 2000, they made a supplementary analysis. In the two analyses, * * * identified 303 compounds. In order to test the attractiveness of these 303 compounds to mosquitoes, they designed a special odor measuring device for experimental study. More than 20 years ago, technicians from the Insect Research Center found that the residue left on the glass when touching it with their hands can attract mosquitoes. The attraction of cultured blood with sweat stains to mosquitoes can last for up to 6 hours. They used this bait instead of human arm as a standard to compare the lure performance of each component. After a large number of combination matching tests on the composition and content of sweat volatiles, they found that the mixture of lactic acid, acetone and dimethyl disulfide was particularly attractive to mosquitoes. Acetone is a component released when the human body metabolizes fat. Dimethyl disulfide is a component released when bacteria decompose protein. When these three ingredients are used alone, they are only moderately attractive to mosquitoes. For example, lactic acid can only attract less than 20% of mosquitoes; When mixed with tung oil, it can attract 80% mosquitoes. However, this does not exceed the attraction of human arms to mosquitoes. Dimethyl disulfide is the main component of attractant. After adding this ingredient to binary mixture, it becomes more attractive to mosquitoes than some people. This is the first successful example found in the experiment of artificially preparing attractants. Their research goal is to prepare a more attractive attractant to let mosquitoes leave people and enter traps to kill mosquitoes. According to their research, most people excrete basically the same metabolites, but the amount of each compound varies from person to person. This also explains why mosquitoes have different preferences when biting people. However, it is not clear how these substances attract mosquitoes through interaction. For example, some compounds have different attractive forces at different concentrations; It is attractive at a very low concentration, but it does not increase at a high concentration. Mixing acetone, lactic acid and dimethyl disulfide at will is not a good attractant. Therefore, there is still a lot of work to be done to get better attractants. After the research team led by Bernard discovered an attractant equivalent to human sweat secretion, they also knew how to find a mosquito repellent. They found a mosquito repellent compound by adding other compounds to the attractant to make mosquitoes avoid it. This compound can reduce the activity of mosquito attractant by 6%. Unlike the mosquito repellent sold in the United States, the mosquito repellent only works when the mosquito approaches or touches the skin. This compound makes the mosquito feel the presence of the target. For example, when releasing this compound in the air and then reaching out to experimental mosquitoes, most mosquitoes don't even feel someone's arm there. Their sensory organs are obviously disturbed. For patent reasons, they didn't report the name of this compound. This research result will contribute to the progress of mosquito control research, and develop more and safer mosquito repellent no1virtual large-scale dating platform: www.d1xn.com.
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